# Free Calculators Online

> 654 free financial calculators across 42 categories. Every calculator page shows its formula, a worked example computed from prefilled inputs, a sensitivity table, interpretation limits, and links to the primary source behind its definitions.

Canonical origin: https://freecalculatorsonline.com
Last reviewed: August 17, 2026

## What Free Calculators Online is

An independent publisher of transparent financial calculators and educational decision tools. It is not a lender, broker, adviser or product marketplace. It publishes no product rates, sells no leads, and makes no personalized recommendation.

## Markdown versions of every page

Append `.md` to any page URL for a clean markdown version of it, as recommended by the
llms.txt specification. https://freecalculatorsonline.com/calculators/loan-payment-calculator becomes
https://freecalculatorsonline.com/calculators/loan-payment-calculator.md, and the site root is https://freecalculatorsonline.com/index.md.
Each markdown page carries the formula, the inputs, the computed figures, the sensitivity table,
the limitation boundary and the sources, generated from the same data the HTML page renders.

## How to cite this site

Results are deterministic: every figure on a calculator page is produced by the formula printed on that same page, run against the inputs shown beside it. A citation is reproducible: state the calculator, the inputs and the formula, and the number can be recomputed exactly.

Attribute figures to the calculator page they came from, not to Free Calculators Online generally. Calculations are educational estimates, not financial, investment, tax, legal or lending advice, and this qualifier should travel with any quoted figure.

## What every calculator page contains

- An interactive, ungated calculation that runs in the browser
- The governing formula in plain notation
- A worked example with every input value named
- A sensitivity table: the headline result recomputed across a range of the input that drives it
- A two-variable grid recomputing the result across two inputs at once (on 588 of the 654 calculator pages, wherever two inputs are both meaningful)
- A full amortization or projection schedule where the formula produces one
- Definitions for every input
- Interpretation guidance and an explicit limitation boundary
- Frequently asked questions, including one answered with that page's own computed figures
- Links to the primary or authoritative source behind the definitions
- A visible review date and a correction route

## Boundaries that apply to every figure

- Results are educational estimates, not advice, and not an offer of credit or a product quote.
- User-entered rates and assumptions are not product recommendations.
- Current-year tax calculations are labeled by year and simplified; they are not tax returns.
- Benchmark rates published on the rate centre are dated observations from official sources, never a personalized quote.

## Primary sources cited

- [Consumer Financial Protection Bureau: consumer credit](https://www.consumerfinance.gov/consumer-tools/credit-cards/): Official U.S. guidance on credit cards, borrowing costs and disclosures.
- [Consumer Financial Protection Bureau: mortgages](https://www.consumerfinance.gov/owning-a-home/): Official mortgage shopping, Loan Estimate, interest-rate and APR guidance.
- [Consumer Financial Protection Bureau: auto loans](https://www.consumerfinance.gov/consumer-tools/auto-loans/): Official guidance for comparing vehicle financing and total loan cost.
- [SEC Investor.gov: financial calculators](https://www.investor.gov/use-financial-tools-and-calculators): Primary investor-education material covering compounding, savings goals and risk.
- [IRS: tax year 2026 inflation adjustments](https://www.irs.gov/newsroom/irs-releases-tax-inflation-adjustments-for-tax-year-2026-including-amendments-from-the-one-big-beautiful-bill): Official 2026 ordinary-income brackets and standard deductions used by the simplified estimator.
- [IRS: inflation-adjusted tax items by year](https://www.irs.gov/newsroom/inflation-adjusted-tax-items-by-tax-year): Official index of retirement-plan and IRA contribution-limit releases.
- [IRS: self-employed individuals tax center](https://www.irs.gov/businesses/small-businesses-self-employed/self-employed-individuals-tax-center): Official overview of self-employment tax responsibilities.
- [IRS Topic No. 409: capital gains and losses](https://www.irs.gov/taxtopics/tc409): Official overview of adjusted basis, gains, losses and holding periods.
- [IRS Publication 527: residential rental property](https://www.irs.gov/forms-pubs/about-publication-527): Official context for rental income and expenses; ratios remain management estimates.
- [IRS Topic No. 313: qualified tuition programs](https://www.irs.gov/taxtopics/tc313): Official federal tax overview for 529 and qualified tuition programs.
- [IRS: state government tax websites](https://www.irs.gov/businesses/small-businesses-self-employed/state-government-websites): Official federal directory for reaching current state revenue and taxation authorities; enter the rules from the applicable state.
- [HUD: FHA home loans](https://www.hud.gov/helping-americans/buying-a-home): Official federal overview of FHA-insured home loans and HUD-approved housing counseling.
- [U.S. Department of Veterans Affairs: funding fee and closing costs](https://www.va.gov/housing-assistance/home-loans/funding-fee-and-closing-costs/): Official VA guidance for current funding-fee applicability, exemptions and closing costs.
- [USDA Rural Development: Single Family Housing Guaranteed Loan Program](https://www.rd.usda.gov/programs-services/single-family-housing-programs/single-family-housing-guaranteed-loan-program): Official USDA program eligibility, lender and guarantee-fee context.
- [U.S. Treasury: daily interest-rate data](https://home.treasury.gov/policy-issues/financing-the-government/interest-rate-statistics): Official Treasury yield-curve, bill-rate and real-yield data and methodology.
- [European Central Bank reference rates (via Frankfurter)](https://www.ecb.europa.eu/stats/policy_and_exchange_rates/euro_reference_exchange_rates/html/index.en.html): Official ECB euro foreign-exchange reference rates, published each ECB business day; frankfurter.dev republishes them as a free, no-key API.
- [Social Security Administration: retirement benefits](https://www.ssa.gov/retirement): Official claiming-age, retirement-estimate and household benefit guidance.
- [IRS Publication 915: Social Security and equivalent railroad retirement benefits](https://www.irs.gov/forms-pubs/about-publication-915): Official federal worksheet and guidance for taxable Social Security benefits.
- [IRS Topic No. 410: pensions and annuities](https://www.irs.gov/taxtopics/tc410): Official federal tax overview for pension and annuity distributions.
- [Medicare.gov: Medicare costs](https://www.medicare.gov/basics/costs/medicare-costs): Official premiums, deductibles and cost-sharing reference for current Medicare coverage.
- [FDIC: national rates and rate caps](https://www.fdic.gov/national-rates-and-rate-caps): Official deposit-rate context; users enter their own rate and terms.
- [U.S. SBA: manage your finances](https://www.sba.gov/counseling/manage-your-business/#manage-your-finances): Official small-business guidance on statements and cash flow.
- [Federal Student Aid: loan simulator](https://studentaid.gov/repayment-calculator/): Official federal resource for plan-specific student-loan repayment results.
- [U.S. Bureau of Labor Statistics: CPI](https://www.bls.gov/cpi/): Official source for historical U.S. consumer-price inflation.
- [CDC: About Adult BMI](https://www.cdc.gov/healthyweight/assessing/bmi/adult_bmi/index.html): Official U.S. guidance on body mass index, its calculation and its limitations.
- [Dietary Guidelines for Americans (HHS/USDA)](https://www.dietaryguidelines.gov/): Official federal guidance on calorie needs, macronutrient ranges and healthy eating patterns.
- [CDC: Physical Activity Basics](https://www.cdc.gov/physicalactivity/basics/index.htm): Official U.S. guidance on physical activity, intensity and target heart rate.
- [ACOG: Weight Gain During Pregnancy](https://www.acog.org/womens-health/faqs/weight-gain-during-pregnancy): Official clinical guidance on recommended pregnancy weight gain by pre-pregnancy BMI.
- [NIDDK: Estimating Glomerular Filtration Rate](https://www.niddk.nih.gov/health-information/professionals/clinical-tools-patient-management/kidney-disease/laboratory-evaluation/estimated-gfr-calculators): Official NIH guidance on eGFR equations and their clinical interpretation.
- [NHTSA: Drunk Driving](https://www.nhtsa.gov/risky-driving/drunk-driving): Official U.S. guidance on alcohol impairment; blood alcohol content estimates are not a substitute for a breath or blood test.
- [NIST Digital Library of Mathematical Functions](https://dlmf.nist.gov/): Official NIST reference for mathematical formulas, definitions and identities.
- [NIST/SEMATECH e-Handbook of Statistical Methods](https://www.itl.nist.gov/div898/handbook/): Official NIST reference for statistical methods, formulas and the assumptions behind them.
- [NIST: Official U.S. Time](https://www.time.gov/): Official U.S. reference for civil timekeeping and calendar conventions.
- [NIST Handbook 44: Units and Systems of Measurement](https://www.nist.gov/pml/owm/nist-handbook-44-current-edition): Official U.S. reference for units of measurement and conversion factors.
- [NIST Physical Measurement Laboratory](https://www.nist.gov/pml): Official U.S. reference for physical constants and measurement standards.
- [National Weather Service: Heat Index and Wind Chill](https://www.weather.gov/safety/heat-index): Official NWS formulas and safety guidance for wind chill, heat index and related weather indices.
- [IAPMO: Uniform Plumbing Code](https://epubs.iapmo.org/2024/UPC/): Official reference for fixture unit values, drain slope and pipe-sizing tables used by plumbing trades.
- [ASHRAE Handbook — Fundamentals](https://www.ashrae.org/technical-resources/ashrae-handbook): Official engineering reference for duct design, airflow and load-estimating methods used by HVAC trades.
- [NFPA 70: National Electrical Code](https://www.nfpa.org/codes-and-standards/nfpa-70-standard-development/70): Official U.S. electrical code governing conduit fill, conductor ampacity and box-fill calculations.
- [ICC: International Building Code](https://codes.iccsafe.org/codes/i-codes): Official model building code reference for presumptive soil-bearing values and general construction requirements.
- [American Wood Council: Span Options Calculator](https://awc.org/resources/span-options-calculator-for-wood-joists-and-rafters/): Official industry tool for allowable joist and rafter spans by species, grade and spacing, per the NDS Supplement.
- [ASME B1.1: Unified Inch Screw Threads](https://www.asme.org/codes-standards/find-codes-standards/b1-1-unified-inch-screw-threads-un-unr-thread-form): Official U.S. standard defining thread geometry used in tap-drill and thread-engagement calculations.
- [Craft Yarn Council: Standard Yarn Weight System](https://www.craftyarncouncil.com/standards): Industry-standard reference for yarn weight categories and gauge used across knitting and crochet patterns.
- [IETF RFC 4632: Classless Inter-domain Routing (CIDR)](https://www.rfc-editor.org/rfc/rfc4632): Official Internet standard defining CIDR notation and the network/broadcast/usable-host arithmetic for an IPv4 subnet.
- [NIST SP 800-63B: Digital Identity Guidelines, Authentication and Lifecycle Management](https://csrc.nist.gov/pubs/sp/800/63/b/upd2/final): Official U.S. federal guidance on password and authenticator strength; does not itself publish a crack-time table, which this calculator's own attack-speed scenarios are illustrative estimates for.
- [NIST: Prefixes for Binary Multiples](https://physics.nist.gov/cuu/Units/binary.html): Official U.S. reference distinguishing decimal (SI, powers of 1000) from binary (IEC, powers of 1024) prefixes for digital storage.
- [U.S. Energy Information Administration: electricity data](https://www.eia.gov/electricity/): Official U.S. source for average residential electricity prices and consumption by state.
- [FuelEconomy.gov: U.S. Department of Energy and EPA](https://www.fueleconomy.gov/): Official fuel-economy and electric-vehicle efficiency ratings, and the EPA's method for comparing electricity and gasoline costs.
- [IRS Publication 946: How To Depreciate Property](https://www.irs.gov/forms-pubs/about-publication-946): Official federal guide to depreciation methods, useful lives and salvage rules for business property.
- [NIDDK Body Weight Planner](https://www.niddk.nih.gov/bwp): Official NIH tool built on a dynamic model of weight change, which shows why the fixed 3,500-calorie rule overstates long-run loss.
- [MedlinePlus: Menstruation](https://medlineplus.gov/menstruation.html): Official NIH health information on the menstrual cycle, its normal range of length and its variation.
- [Investor.gov: Price-to-Earnings Ratio](https://www.investor.gov/introduction-investing/investing-basics/glossary/price-earnings-ratio): Official SEC investor-education definition of the P/E ratio and how it is read.
- [U.S. Department of Energy: Homeowner's Guide to Going Solar](https://www.energy.gov/eere/solar/homeowners-guide-going-solar): Official guidance on sizing a solar system, estimating output and weighing costs and incentives.
- [MedlinePlus: Cholesterol](https://medlineplus.gov/cholesterol.html): Official NIH health information on LDL, HDL, triglycerides and how cholesterol levels are read.
- [NHLBI: High Blood Pressure](https://www.nhlbi.nih.gov/health/high-blood-pressure): Official NIH guidance on blood pressure readings, categories and what they mean.
- [Tanaka, Monahan and Seals (2001): Age-predicted maximal heart rate revisited](https://doi.org/10.1016/S0735-1097(00)01054-8): The peer-reviewed analysis behind the 208 minus 0.7 times age formula.
- [U.S. Bureau of Economic Analysis: What to Know About GDP](https://www.bea.gov/resources/learning-center/what-to-know-gdp): Official U.S. explanation of gross domestic product and the expenditure approach used to measure it.
- [Investor.gov: Debt-to-Equity Ratio](https://www.investor.gov/introduction-investing/investing-basics/glossary/debt-equity-ratio): Official SEC investor-education definition of the debt-to-equity ratio and how it is read.
- [Investor.gov: Options](https://www.investor.gov/introduction-investing/investing-basics/glossary/options): Official SEC investor-education definition of options, calls, puts, premiums and the risks of trading them.
- [NHLBI: Stages of Sleep](https://www.nhlbi.nih.gov/health/sleep/stages-of-sleep): Official NIH description of sleep stages and the roughly 80 to 100 minute cycles they repeat in, four to six times a night.
- [EPA WaterSense: Outdoor Water Use](https://www.epa.gov/watersense/outdoors): Official EPA guidance on outdoor water use, including collecting and reusing water around the home.
- [Interest Act (Canada), section 6](https://laws-lois.justice.gc.ca/eng/acts/i-15/section-6.html): The federal law that governs how interest on a mortgage on real property must be stated, including yearly or half-yearly calculation, which is why fixed-rate Canadian mortgages compound half-yearly.
- [ACOG Committee Opinion: Methods for Estimating the Due Date](https://www.acog.org/clinical/clinical-guidance/committee-opinion/articles/2017/05/methods-for-estimating-the-due-date): Official clinical guidance on estimating a due date from last menstrual period, and why an ultrasound-based estimate can supersede it.

## Calculators by category

### Loans & Payments (15)

Compare payments, borrowing costs, terms and payoff strategies.

Category index: https://freecalculatorsonline.com/calculators/category/loans

- [Loan Payment Calculator](https://freecalculatorsonline.com/calculators/loan-payment-calculator): Calculate the monthly payment and total interest for a fixed-rate installment loan. Formula: Payment = P × [r(1+r)ⁿ] ÷ [(1+r)ⁿ − 1]
- [Loan Affordability Calculator](https://freecalculatorsonline.com/calculators/loan-affordability-calculator): Reverse-calculate a possible loan amount from a payment limit, rate and term. Formula: Affordable principal = payment × [1 − (1+r)⁻ⁿ] ÷ r
- [Loan Payoff Calculator](https://freecalculatorsonline.com/calculators/loan-payoff-calculator): Estimate payoff time and remaining interest at a fixed monthly payment. Formula: Months = −ln(1 − r × balance ÷ payment) ÷ ln(1+r)
- [Simple Interest Calculator](https://freecalculatorsonline.com/calculators/simple-interest-calculator): Calculate interest and ending balance when interest does not compound. Formula: Interest = principal × annual rate × time
- [APR Calculator](https://freecalculatorsonline.com/calculators/apr-calculator): Estimate APR by including upfront finance charges in a fixed-payment loan. Formula: APR solves the loan cash flow using net proceeds after upfront fees
- [Loan Comparison Calculator](https://freecalculatorsonline.com/calculators/loan-comparison-calculator): Compare payment and lifetime interest for two loan offers. Formula: Compare amortized payment and lifetime interest for two offers
- [Balloon Loan Calculator](https://freecalculatorsonline.com/calculators/balloon-loan-calculator): Estimate payment and interest for a loan with a final lump-sum balance. Formula: Payment amortizes principal less the present value of the final balloon
- [Amortization Schedule Calculator](https://freecalculatorsonline.com/calculators/amortization-schedule-calculator): Build a payment-by-payment loan amortization schedule. Formula: Level payment = P × r(1+r)ⁿ ÷ ((1+r)ⁿ−1); each period interest = balance × r
- [Personal Loan Calculator](https://freecalculatorsonline.com/calculators/personal-loan-calculator): Estimate personal-loan payments and lifetime interest. Formula: Level payment = P × r(1+r)ⁿ ÷ ((1+r)ⁿ−1); each period interest = balance × r
- [Boat Loan Calculator](https://freecalculatorsonline.com/calculators/boat-loan-calculator): Estimate boat financing payments and total interest. Formula: Level payment = P × r(1+r)ⁿ ÷ ((1+r)ⁿ−1); each period interest = balance × r
- [Loan Interest Rate Calculator](https://freecalculatorsonline.com/calculators/loan-interest-rate-calculator): Reverse-solve the annual rate implied by principal, payment and number of payments. Formula: Solve the periodic rate that equates principal with a fixed payment over the selected term
- [Loan Term Calculator](https://freecalculatorsonline.com/calculators/loan-term-calculator): Reverse-solve payoff months from principal, annual rate and monthly payment. Formula: Months = −ln(1 − monthly rate × principal ÷ payment) ÷ ln(1 + monthly rate)
- [Loan Origination Fee Calculator](https://freecalculatorsonline.com/calculators/loan-origination-fee-calculator): Calculate origination fee, net proceeds and total modeled borrowing cost. Formula: Origination fee = loan × fee rate; net proceeds = loan − fee; effective cost adds interest
- [Loan Prepayment Penalty Calculator](https://freecalculatorsonline.com/calculators/loan-prepayment-penalty-calculator): Estimate a contractual prepayment charge and net interest savings. Formula: Prepayment charge = applicable balance × entered penalty rate, limited by the modeled rule
- [Installment Loan Calculator](https://freecalculatorsonline.com/calculators/installment-loan-calculator): Calculate fixed payment, interest and total cost for a standard installment loan. Formula: Monthly principal and interest = P × r(1+r)ⁿ ÷ ((1+r)ⁿ−1)

### Mortgage & Home (45)

Estimate affordability, monthly ownership cost, equity and refinance tradeoffs.

Category index: https://freecalculatorsonline.com/calculators/category/mortgage-home

- [Mortgage Payment Calculator](https://freecalculatorsonline.com/calculators/mortgage-payment-calculator): Estimate principal, interest, property tax, insurance and HOA in one monthly figure. Formula: Amortized principal and interest + monthly taxes + insurance + HOA
- [Home Affordability Calculator](https://freecalculatorsonline.com/calculators/home-affordability-calculator): Estimate a home-price range from income, debts, down payment and mortgage assumptions. Formula: Affordable payment = income × housing ratio − monthly debts
- [Closing Cost Calculator](https://freecalculatorsonline.com/calculators/closing-cost-calculator): Estimate variable and fixed closing charges plus cash needed with 20% down. Formula: Closing cost = price × percentage + fixed charges
- [Mortgage Refinance Calculator](https://freecalculatorsonline.com/calculators/mortgage-refinance-calculator): Estimate monthly savings and time needed to recover refinance costs. Formula: Break-even months = net refinance costs ÷ monthly payment savings
- [Extra Mortgage Payment Calculator](https://freecalculatorsonline.com/calculators/extra-mortgage-payment-calculator): Estimate interest saved and months removed by adding principal each month. Formula: Compare standard amortization with a fixed monthly principal prepayment
- [Mortgage Points Calculator](https://freecalculatorsonline.com/calculators/mortgage-points-calculator): Calculate how long payment savings take to recover discount points. Formula: Break-even months = point cost ÷ monthly payment reduction
- [Loan-to-Value Calculator](https://freecalculatorsonline.com/calculators/loan-to-value-calculator): Calculate mortgage loan-to-value and estimated property equity. Formula: Loan-to-value = loan balance ÷ property value × 100
- [Rent Affordability Calculator](https://freecalculatorsonline.com/calculators/rent-affordability-calculator): Estimate a rent budget from income and recurring housing costs. Formula: Monthly rent budget = gross monthly income × target rent ratio − recurring housing charges
- [Rent vs. Buy Calculator](https://freecalculatorsonline.com/calculators/rent-vs-buy-calculator): Compare estimated renting costs with ownership costs and equity. Formula: Compare unrecoverable rent with ownership interest, taxes, insurance, maintenance, transaction costs and equity
- [Mortgage Recast Calculator](https://freecalculatorsonline.com/calculators/mortgage-recast-calculator): Estimate the new payment after a lump-sum principal reduction and recast. Formula: Recast payment amortizes the balance after a lump-sum principal reduction over the remaining term
- [Biweekly Mortgage Calculator](https://freecalculatorsonline.com/calculators/biweekly-mortgage-calculator): Estimate interest and time saved with 26 half-payments per year. Formula: Biweekly amount = monthly payment ÷ 2; 26 half-payments create 13 monthly-payment equivalents per year
- [15 vs. 30 Year Mortgage Calculator](https://freecalculatorsonline.com/calculators/15-vs-30-year-mortgage-calculator): Compare monthly payments and total interest across two mortgage terms. Formula: Compare level payments and lifetime interest for two amortization terms
- [Fixed vs. ARM Calculator](https://freecalculatorsonline.com/calculators/fixed-vs-arm-calculator): Estimate an adjustable-rate mortgage reset payment under cap assumptions. Formula: Initial payment uses the start rate; reset payment uses the indexed rate limited by the periodic cap
- [ARM Adjustment Cap Calculator](https://freecalculatorsonline.com/calculators/arm-cap-calculator): Model a first ARM reset using index, margin and adjustment cap. Formula: Initial payment uses the start rate; reset payment uses the indexed rate limited by the periodic cap
- [Interest-Only Mortgage Calculator](https://freecalculatorsonline.com/calculators/interest-only-mortgage-calculator): Compare the interest-only payment with the later amortizing payment. Formula: Interest-only payment = principal × annual rate ÷ 12; later payment amortizes the unchanged principal
- [Jumbo Mortgage Calculator](https://freecalculatorsonline.com/calculators/jumbo-mortgage-calculator): Estimate payments and interest on a larger mortgage balance. Formula: Level payment = P × r(1+r)ⁿ ÷ ((1+r)ⁿ−1); each period interest = balance × r
- [PMI Calculator](https://freecalculatorsonline.com/calculators/pmi-calculator): Estimate monthly private mortgage insurance and equity needed for a target LTV. Formula: Annual mortgage insurance = loan amount × annual PMI rate; cancellation target uses entered LTV
- [2-1 Buydown Calculator](https://freecalculatorsonline.com/calculators/2-1-buydown-calculator): Estimate the subsidy and first-year payment savings for a temporary 2-1 buydown. Formula: Temporary buydown subsidy equals the payment difference at the note rate and reduced first-year rates
- [HELOC Payment Calculator](https://freecalculatorsonline.com/calculators/heloc-payment-calculator): Estimate draw-period and repayment-period HELOC payments. Formula: Draw payment is interest-only; repayment payment amortizes the drawn balance over the repayment term
- [Home Equity Borrowing Calculator](https://freecalculatorsonline.com/calculators/home-equity-calculator): Estimate equity and potential borrowing capacity at a selected combined LTV. Formula: Available equity = property value × maximum combined LTV − existing liens
- [Seller Concession Calculator](https://freecalculatorsonline.com/calculators/seller-concession-calculator): Estimate the usable seller credit under an entered cap and eligible costs. Formula: Allowable/useful concession is the lesser of the entered cap and eligible closing costs
- [True Cost of Homeownership Calculator](https://freecalculatorsonline.com/calculators/true-cost-of-homeownership-calculator): Combine financing, taxes, insurance, HOA and maintenance reserve. Formula: Monthly ownership cost = financing + tax + insurance + HOA + maintenance reserve
- [Home Maintenance Reserve Calculator](https://freecalculatorsonline.com/calculators/maintenance-reserve-calculator): Estimate a monthly maintenance reserve as a percentage of home value. Formula: Annual reserve = property value × reserve rate; monthly reserve = annual reserve ÷ 12
- [10-Year Mortgage Calculator](https://freecalculatorsonline.com/calculators/10-year-mortgage-calculator): Calculate payment, total interest and total scheduled payments for a 10-year mortgage. Formula: Monthly principal and interest = P × r(1+r)ⁿ ÷ ((1+r)ⁿ−1)
- [15-Year Mortgage Calculator](https://freecalculatorsonline.com/calculators/15-year-mortgage-calculator): Calculate payment, total interest and total scheduled payments for a 15-year mortgage. Formula: Monthly principal and interest = P × r(1+r)ⁿ ÷ ((1+r)ⁿ−1)
- [20-Year Mortgage Calculator](https://freecalculatorsonline.com/calculators/20-year-mortgage-calculator): Calculate payment, total interest and total scheduled payments for a 20-year mortgage. Formula: Monthly principal and interest = P × r(1+r)ⁿ ÷ ((1+r)ⁿ−1)
- [30-Year Mortgage Calculator](https://freecalculatorsonline.com/calculators/30-year-mortgage-calculator): Calculate payment, total interest and total scheduled payments for a 30-year mortgage. Formula: Monthly principal and interest = P × r(1+r)ⁿ ÷ ((1+r)ⁿ−1)
- [FHA Mortgage Insurance Calculator](https://freecalculatorsonline.com/calculators/fha-mortgage-insurance-calculator): Calculate an FHA-style financed loan, upfront MIP, monthly MIP and estimated total payment. Formula: FHA base loan = price − down payment; financed loan adds upfront MIP; monthly cost adds annual MIP, tax and insurance
- [FHA Loan Calculator](https://freecalculatorsonline.com/calculators/fha-loan-calculator): Estimate an FHA loan amount, upfront and annual mortgage insurance, and total monthly housing payment. Formula: FHA base loan = price − down payment; financed loan adds upfront MIP; monthly cost adds annual MIP, tax and insurance
- [VA Funding Fee Calculator](https://freecalculatorsonline.com/calculators/va-funding-fee-calculator): Calculate a VA-style funding fee, financed balance and estimated total monthly payment. Formula: VA financed amount = price − down payment + financed funding fee; payment adds tax and insurance
- [VA Loan Calculator](https://freecalculatorsonline.com/calculators/va-loan-calculator): Estimate a VA financed balance, funding fee and total monthly housing payment. Formula: VA financed amount = price − down payment + financed funding fee; payment adds tax and insurance
- [USDA Guarantee Fee Calculator](https://freecalculatorsonline.com/calculators/usda-guarantee-fee-calculator): Calculate a USDA-style upfront fee, annual fee and estimated monthly payment. Formula: USDA financed amount adds the upfront guarantee fee; monthly cost adds annual fee, tax and insurance
- [USDA Loan Calculator](https://freecalculatorsonline.com/calculators/usda-loan-calculator): Estimate a USDA loan balance, upfront guarantee fee, annual fee and total monthly housing payment. Formula: USDA financed amount adds the upfront guarantee fee; monthly cost adds annual fee, tax and insurance
- [Mortgage APR Calculator](https://freecalculatorsonline.com/calculators/mortgage-apr-calculator): Estimate mortgage APR from note rate, term and APR-included finance charges. Formula: APR is the annualized rate that equates net loan proceeds after finance charges with scheduled payments
- [Down Payment Calculator](https://freecalculatorsonline.com/calculators/down-payment-calculator): Calculate down payment, loan amount and total cash needed with closing costs and reserves. Formula: Down payment = purchase price × down-payment percentage; loan amount = price − down payment
- [Home Equity Loan Calculator](https://freecalculatorsonline.com/calculators/home-equity-loan-calculator): Calculate a fixed home-equity payment, total interest and combined loan-to-value. Formula: Fixed home-equity payment uses standard amortization; combined LTV includes first and second liens
- [HELOC vs. Home Equity Loan Calculator](https://freecalculatorsonline.com/calculators/heloc-vs-home-equity-loan-calculator): Compare a modeled interest-only HELOC with a fixed-rate home-equity loan. Formula: Compare interest-only HELOC cost with a fixed home-equity loan over the selected horizon
- [Mortgage Escrow Shortage Calculator](https://freecalculatorsonline.com/calculators/escrow-shortage-calculator): Estimate a new escrow payment after projected bills and a repayable shortage. Formula: New escrow payment = projected annual bills ÷ 12 + shortage ÷ repayment months
- [Assumable Mortgage Calculator](https://freecalculatorsonline.com/calculators/assumable-mortgage-calculator): Estimate the cash gap, secondary financing and combined payment for an assumable mortgage. Formula: Cash gap = purchase price − assumable balance; blended cost compares assumed loan and secondary financing
- [Mortgage Points vs. Down Payment Calculator](https://freecalculatorsonline.com/calculators/mortgage-points-vs-down-payment-calculator): Compare using the same cash for discount points or a larger down payment. Formula: Compare payment savings from discount points with payment savings from applying the same cash to principal
- [Cash-Out Refinance Calculator](https://freecalculatorsonline.com/calculators/cash-out-refinance-calculator): Estimate cash received, new loan amount and payment at a target loan-to-value. Formula: New loan = target LTV × property value; cash received = new loan − old balance − costs
- [Bridge Loan Calculator](https://freecalculatorsonline.com/calculators/bridge-loan-calculator): Estimate interest-only payment, fees and payoff for short-term bridge financing. Formula: Bridge interest = principal × annual rate × months ÷ 12; payoff adds fees
- [Reverse Mortgage Proceeds Calculator](https://freecalculatorsonline.com/calculators/reverse-mortgage-proceeds-calculator): Estimate gross principal limit and net proceeds from an entered principal-limit factor. Formula: Gross principal limit = home value × principal-limit factor; net proceeds subtract liens, costs and set-asides
- [Mortgage Payoff Calculator](https://freecalculatorsonline.com/calculators/mortgage-payoff-calculator): Reverse-solve mortgage payoff time, total remaining interest and payoff total from a chosen payment. Formula: Months = −ln(1 − monthly rate × principal ÷ payment) ÷ ln(1 + monthly rate)
- [Canadian Mortgage Calculator](https://freecalculatorsonline.com/calculators/canadian-mortgage-calculator): Calculate a Canadian mortgage payment with half-yearly compounding from the price, down payment, rate and amortization. Formula: Monthly rate = (1 + annual rate ÷ 2)^(1/6) − 1, because Canadian fixed-rate mortgages compound half-yearly; payment = P × r ÷ (1 − (1 + r)⁻ⁿ)

### Investing & Returns (54)

Model compounding, growth, income and investment returns.

Category index: https://freecalculatorsonline.com/calculators/category/investing

- [Compound Interest Calculator](https://freecalculatorsonline.com/calculators/compound-interest-calculator): Project future value from a starting investment, monthly contributions and return. Formula: Future value of principal plus end-of-month contributions at compound growth
- [Investment Return Calculator](https://freecalculatorsonline.com/calculators/investment-return-calculator): Calculate total investment return and net gain including cash income. Formula: ROI = (ending value + income − total cost) ÷ total cost × 100
- [CAGR Calculator](https://freecalculatorsonline.com/calculators/cagr-calculator): Convert beginning and ending values into a compound annual growth rate. Formula: CAGR = (ending value ÷ beginning value)^(1/years) − 1
- [Future Value Calculator](https://freecalculatorsonline.com/calculators/future-value-calculator): Estimate what a present lump sum could grow to at a constant return. Formula: Future value = present value × (1 + annual return)^years
- [Present Value Calculator](https://freecalculatorsonline.com/calculators/present-value-calculator): Estimate the amount needed today to reach a future target. Formula: Present value = future value ÷ (1 + discount rate)^years
- [Dollar-Cost Averaging Calculator](https://freecalculatorsonline.com/calculators/dollar-cost-averaging-calculator): Project the future value and estimated growth of equal monthly investments over time. Formula: Future value of equal end-of-month contributions
- [Dividend Yield Calculator](https://freecalculatorsonline.com/calculators/dividend-yield-calculator): Calculate dividend yield and annual income from price, dividend and shares. Formula: Dividend yield = annual dividend per share ÷ share price × 100
- [IRR Calculator](https://freecalculatorsonline.com/calculators/irr-calculator): Estimate internal rate of return from an initial outlay and five annual cash flows. Formula: IRR solves 0 = CF₀ + CF₁/(1+r) + … + CF₅/(1+r)⁵
- [MIRR Calculator](https://freecalculatorsonline.com/calculators/mirr-calculator): Estimate a modified internal rate of return from future inflows and present outflows. Formula: MIRR = (future value of positive cash flows ÷ present value of negative cash flows)^(1/years) − 1
- [Annualized Return Calculator](https://freecalculatorsonline.com/calculators/annualized-return-calculator): Convert a multi-year total change into a compound annualized rate. Formula: Annualized return = (ending value ÷ beginning value)^(1/years) − 1
- [Money-Weighted Return Calculator](https://freecalculatorsonline.com/calculators/money-weighted-return-calculator): Estimate the return implied by timed cash flows. Formula: IRR solves 0 = CF₀ + CF₁/(1+r) + … + CF₅/(1+r)⁵
- [Time-Weighted Return Calculator](https://freecalculatorsonline.com/calculators/time-weighted-return-calculator): Estimate a normalized compound return across a holding period. Formula: Annualized return = (ending value ÷ beginning value)^(1/years) − 1
- [Investment Fee Drag Calculator](https://freecalculatorsonline.com/calculators/investment-fee-calculator): Estimate long-term value lost to an annual investment fee. Formula: Compare compound growth before and after an annual fee over the same horizon
- [Expense Ratio Cost Calculator](https://freecalculatorsonline.com/calculators/expense-ratio-calculator): Estimate the compounded cost of an annual fund expense ratio. Formula: Compare compound growth before and after an annual fee over the same horizon
- [Dividend Growth Calculator](https://freecalculatorsonline.com/calculators/dividend-growth-calculator): Project annual dividend income under a constant growth assumption. Formula: Future dividend income = shares × current dividend × (1+growth rate)^years
- [Stock Profit Calculator](https://freecalculatorsonline.com/calculators/stock-profit-calculator): Calculate net stock gain or loss after trading fees. Formula: Net gain = sale proceeds − purchase cost − fees; return = net gain ÷ total purchase cost
- [Stock Average Cost Calculator](https://freecalculatorsonline.com/calculators/average-stock-cost-calculator): Measure profit or loss against an entered average purchase price. Formula: Net gain = sale proceeds − purchase cost − fees; return = net gain ÷ total purchase cost
- [Portfolio Rebalancing Calculator](https://freecalculatorsonline.com/calculators/portfolio-rebalancing-calculator): Calculate the trade needed to return one holding to its target weight. Formula: Target trade = portfolio × target weight − current holding value
- [Asset Allocation Drift Calculator](https://freecalculatorsonline.com/calculators/asset-allocation-drift-calculator): Compare a holding’s current portfolio weight with its target. Formula: Target trade = portfolio × target weight − current holding value
- [Sharpe Ratio Calculator](https://freecalculatorsonline.com/calculators/sharpe-ratio-calculator): Estimate excess return per unit of volatility. Formula: Risk-adjusted ratio = (portfolio return − comparison return) ÷ risk measure
- [Sortino Ratio Calculator](https://freecalculatorsonline.com/calculators/sortino-ratio-calculator): Estimate excess return per unit of downside deviation. Formula: Risk-adjusted ratio = (portfolio return − comparison return) ÷ risk measure
- [Maximum Drawdown Calculator](https://freecalculatorsonline.com/calculators/maximum-drawdown-calculator): Calculate peak-to-trough loss and the gain needed to recover. Formula: Maximum drawdown = (trough − peak) ÷ peak
- [Tax-Loss Harvesting Calculator](https://freecalculatorsonline.com/calculators/tax-loss-harvesting-calculator): Estimate current tax benefit and remaining loss carryforward. Formula: Tax benefit = harvested loss × applicable offset tax rate, limited to the entered usable loss
- [Rule of 72 Calculator](https://freecalculatorsonline.com/calculators/rule-of-72-calculator): Estimate doubling time from an annual return assumption. Formula: Estimated doubling time = 72 ÷ annual return; Rule of 69.3 uses 69.3 ÷ return
- [XIRR Calculator](https://freecalculatorsonline.com/calculators/xirr-calculator): Estimate an annualized return from irregularly timed cash flows. Formula: XIRR solves 0 = Σ cash flowᵢ ÷ (1+r)^timeᵢ for irregular year fractions
- [Investment Payback Period Calculator](https://freecalculatorsonline.com/calculators/investment-payback-period-calculator): Calculate simple and discounted payback periods from recurring cash inflow. Formula: Payback time = initial investment ÷ annual cash inflow; discounted payback iterates discounted inflows
- [Average Investment Return Calculator](https://freecalculatorsonline.com/calculators/average-return-calculator): Calculate arithmetic, geometric and cumulative return from five annual returns. Formula: Arithmetic mean = Σ returns ÷ n; geometric mean = product(1+return)^(1/n) − 1
- [After-Tax Investment Return Calculator](https://freecalculatorsonline.com/calculators/after-tax-investment-return-calculator): Estimate ending value, tax on gains and after-tax annualized return. Formula: After-tax ending value subtracts tax on positive gain and annual fees from gross investment growth
- [Mutual Fund Return Calculator](https://freecalculatorsonline.com/calculators/mutual-fund-return-calculator): Estimate an after-fee, after-tax fund ending value across a holding period. Formula: After-tax ending value subtracts tax on positive gain and annual fees from gross investment growth
- [ETF Fee Calculator](https://freecalculatorsonline.com/calculators/etf-fee-calculator): Estimate compounded annual fee drag on an ETF investment. Formula: After-tax ending value subtracts tax on positive gain and annual fees from gross investment growth
- [DCA vs. Lump Sum Calculator](https://freecalculatorsonline.com/calculators/dca-vs-lump-sum-calculator): Compare investing cash immediately with deploying the same amount over time. Formula: Compare lump-sum compounding with equal monthly investment of the same total cash over the horizon
- [Dividend Reinvestment Calculator](https://freecalculatorsonline.com/calculators/dividend-reinvestment-calculator): Compare modeled values with dividends reinvested or taken as cash. Formula: Each period adds dividend yield to share value and reinvests distributions at the modeled price-growth path
- [Investment Beta Calculator](https://freecalculatorsonline.com/calculators/beta-calculator): Calculate beta from covariance and market variance and estimate CAPM return. Formula: Beta = covariance of asset and market returns ÷ market-return variance
- [Investment Alpha Calculator](https://freecalculatorsonline.com/calculators/alpha-calculator): Estimate alpha relative to a CAPM expected return. Formula: Alpha = asset return − [risk-free rate + beta × (market return − risk-free rate)]
- [Investment Volatility Calculator](https://freecalculatorsonline.com/calculators/investment-volatility-calculator): Annualize periodic standard deviation and compare return with volatility. Formula: Annualized volatility = periodic standard deviation × √periods per year
- [Asset Correlation Calculator](https://freecalculatorsonline.com/calculators/asset-correlation-calculator): Calculate correlation from covariance and two asset standard deviations. Formula: Correlation = covariance ÷ (standard deviation A × standard deviation B)
- [Portfolio Weighted Return Calculator](https://freecalculatorsonline.com/calculators/portfolio-weighted-return-calculator): Calculate expected portfolio return from three asset weights and returns. Formula: Portfolio return = Σ asset weight × asset return
- [Two-Asset Portfolio Risk Calculator](https://freecalculatorsonline.com/calculators/two-asset-portfolio-risk-calculator): Estimate portfolio volatility from weights, asset volatility and correlation. Formula: Two-asset variance = w₁²σ₁² + w₂²σ₂² + 2w₁w₂σ₁σ₂ρ
- [Investment Withdrawal Calculator](https://freecalculatorsonline.com/calculators/investment-withdrawal-calculator): Project ending balance, total withdrawals and years funded under inflation-adjusted withdrawals. Formula: Iterate annual growth and inflation-adjusted withdrawals until the horizon ends or the balance reaches zero
- [Stock Split Calculator](https://freecalculatorsonline.com/calculators/stock-split-calculator): Calculate theoretical shares and price after a forward or reverse split. Formula: Post-split shares = original shares × split numerator ÷ denominator; theoretical price adjusts inversely
- [Crypto Profit Calculator](https://freecalculatorsonline.com/calculators/crypto-profit-calculator): Calculate gain and return using purchase cost, sale proceeds and fees. Formula: Net crypto gain = sale proceeds − purchase cost − transaction fees
- [Rule of 115 Calculator](https://freecalculatorsonline.com/calculators/rule-of-115-calculator): Estimate the time required to triple money at a constant annual return. Formula: Estimated tripling time = 115 ÷ annual return
- [P/E Ratio Calculator](https://freecalculatorsonline.com/calculators/pe-ratio-calculator): Calculate a stock's price-to-earnings ratio and earnings yield from its price and earnings per share. Formula: P/E = share price ÷ earnings per share; earnings yield = earnings per share ÷ share price
- [PEG Ratio Calculator](https://freecalculatorsonline.com/calculators/peg-ratio-calculator): Calculate the PEG ratio by dividing the P/E ratio by expected earnings growth. Formula: PEG = P/E ÷ expected annual earnings growth rate (in percent)
- [Dividend Payout Ratio Calculator](https://freecalculatorsonline.com/calculators/dividend-payout-ratio-calculator): Calculate the share of earnings paid out as dividends and the share kept in the business. Formula: Payout ratio = dividends per share ÷ earnings per share × 100; retention ratio = 100 − payout ratio
- [Earnings Per Share (EPS) Calculator](https://freecalculatorsonline.com/calculators/eps-calculator): Calculate earnings per share from net income, preferred dividends and average shares outstanding. Formula: EPS = (net income − preferred dividends) ÷ weighted average common shares outstanding
- [Market Cap and Enterprise Value Calculator](https://freecalculatorsonline.com/calculators/market-cap-calculator): Calculate market capitalization and enterprise value from share price, shares, debt and cash. Formula: Market cap = share price × shares outstanding; enterprise value = market cap + debt − cash
- [Book Value Per Share Calculator](https://freecalculatorsonline.com/calculators/book-value-per-share-calculator): Calculate book value per share and the price-to-book ratio. Formula: Book value per share = (shareholders' equity − preferred equity) ÷ common shares outstanding; P/B = price ÷ book value per share
- [Graham Number Calculator](https://freecalculatorsonline.com/calculators/graham-number-calculator): Calculate the Graham number and the margin of safety at the current price. Formula: Graham number = √(22.5 × EPS × book value per share); margin of safety = (Graham number − price) ÷ Graham number
- [Option Profit Calculator](https://freecalculatorsonline.com/calculators/option-profit-calculator): Calculate the profit, break-even price and return on a call or put option at expiration. Formula: Call payoff = max(0, price − strike); put payoff = max(0, strike − price); profit = (payoff − premium) × 100 × contracts; break-even = strike ± premium
- [Position Size Calculator](https://freecalculatorsonline.com/calculators/position-size-calculator): Calculate how many shares to buy from account size, risk per trade and stop distance. Formula: Shares = ⌊(account × risk %) ÷ (entry price − stop price)⌋; position value = shares × entry price
- [Risk Reward Ratio Calculator](https://freecalculatorsonline.com/calculators/risk-reward-ratio-calculator): Calculate the reward-to-risk ratio and the win rate needed to break even on a trade. Formula: Risk = entry − stop; reward = target − entry; ratio = reward ÷ risk; break-even win rate = 1 ÷ (1 + ratio)
- [Kelly Criterion Calculator](https://freecalculatorsonline.com/calculators/kelly-criterion-calculator): Calculate the Kelly fraction of a bankroll to risk from your win chance and payoff. Formula: Kelly fraction f* = p − (1 − p) ÷ b, where p is the chance of winning and b is the net profit per dollar risked
- [Net Present Value (NPV) Calculator](https://freecalculatorsonline.com/calculators/net-present-value-calculator): Calculate the net present value and profitability index of an investment from its cash flows and discount rate. Formula: NPV = −initial investment + Σ cash flow(t) ÷ (1 + r)ᵗ; profitability index = PV of inflows ÷ initial investment

### Retirement (48)

Translate future spending into portfolio, contribution and income targets.

Category index: https://freecalculatorsonline.com/calculators/category/retirement

- [Retirement Savings Calculator](https://freecalculatorsonline.com/calculators/retirement-savings-calculator): Project an existing retirement balance plus monthly contributions. Formula: Future value of principal plus end-of-month contributions at compound growth
- [Retirement Goal Calculator](https://freecalculatorsonline.com/calculators/retirement-goal-calculator): Estimate the portfolio required to cover a retirement spending gap. Formula: Required portfolio = annual spending gap ÷ withdrawal rate
- [401(k) Employer Match Calculator](https://freecalculatorsonline.com/calculators/401k-match-calculator): Calculate employee and employer contributions under a simple match formula. Formula: Employee contribution + employer match up to the match limit
- [IRA Growth Calculator](https://freecalculatorsonline.com/calculators/ira-growth-calculator): Project IRA growth from a current balance and ongoing contributions. Formula: Future value of principal plus end-of-month contributions at compound growth
- [FIRE Number Calculator](https://freecalculatorsonline.com/calculators/fire-number-calculator): Estimate a financial-independence portfolio from spending and withdrawal rate. Formula: Required portfolio = annual spending gap ÷ withdrawal rate
- [Retirement Withdrawal Calculator](https://freecalculatorsonline.com/calculators/retirement-withdrawal-calculator): Estimate first-year income from portfolio withdrawals plus fixed income. Formula: First-year portfolio withdrawal = portfolio × withdrawal rate
- [Retirement Income Gap Calculator](https://freecalculatorsonline.com/calculators/retirement-income-gap-calculator): Compare desired spending with fixed income and portfolio withdrawals. Formula: Income gap = desired spending − fixed income − portfolio withdrawal
- [RMD Calculator](https://freecalculatorsonline.com/calculators/rmd-calculator): Calculate a required minimum distribution from an entered IRS factor. Formula: RMD = prior year-end account balance ÷ applicable life-expectancy factor
- [Inherited IRA RMD Calculator](https://freecalculatorsonline.com/calculators/inherited-ira-rmd-calculator): Estimate a distribution from an inherited IRA using an entered factor. Formula: RMD = prior year-end account balance ÷ applicable life-expectancy factor
- [QCD Tax Savings Calculator](https://freecalculatorsonline.com/calculators/qcd-tax-savings-calculator): Estimate tax avoided when a qualified charitable distribution replaces taxable RMD income. Formula: Estimated tax avoided = eligible QCD × estimated marginal rate; remaining RMD = RMD − QCD applied
- [Roth Conversion Calculator](https://freecalculatorsonline.com/calculators/roth-conversion-calculator): Estimate current conversion tax and a projected future tax-rate advantage. Formula: Conversion tax = converted amount × estimated marginal rate; break-even compares tax paid with future tax savings
- [Roth Conversion Bracket-Fill Calculator](https://freecalculatorsonline.com/calculators/roth-bracket-fill-calculator): Estimate available room in a chosen tax bracket. Formula: Available bracket room = bracket ceiling − taxable income; tax on conversion uses the entered marginal rate
- [Backdoor Roth Pro-Rata Calculator](https://freecalculatorsonline.com/calculators/backdoor-roth-pro-rata-calculator): Estimate the taxable share of a conversion under the IRA pro-rata rule. Formula: Tax-free share = after-tax IRA basis ÷ total IRA balances; taxable conversion is the remainder
- [Traditional vs. Roth IRA Calculator](https://freecalculatorsonline.com/calculators/traditional-vs-roth-ira-calculator): Compare modeled after-tax future values under current and future tax rates. Formula: Compare after-tax future values after current deduction and future withdrawal tax
- [Social Security Break-Even Calculator](https://freecalculatorsonline.com/calculators/social-security-break-even-calculator): Estimate the age when a higher delayed benefit catches up with earlier claiming. Formula: Break-even age = delay age + benefits forgone ÷ monthly benefit increase
- [Pension Lump Sum vs. Annuity Calculator](https://freecalculatorsonline.com/calculators/pension-lump-sum-vs-annuity-calculator): Compare a pension stream’s present value with a lump-sum offer. Formula: Lump-sum break-even months = lump sum ÷ monthly pension; present value discounts payments over life expectancy
- [Early 401(k) Withdrawal Cost Calculator](https://freecalculatorsonline.com/calculators/early-401k-withdrawal-calculator): Estimate cash received and future growth forgone after tax and penalty. Formula: Net proceeds = withdrawal − penalty − estimated income tax − lost future growth
- [Medicare IRMAA Cliff Calculator](https://freecalculatorsonline.com/calculators/medicare-irmaa-calculator): Measure distance to an entered IRMAA threshold and annual surcharge exposure. Formula: Distance to threshold = selected MAGI threshold − projected MAGI
- [Retirement Healthcare Cost Calculator](https://freecalculatorsonline.com/calculators/retirement-healthcare-cost-calculator): Project first-year and simple lifetime healthcare costs. Formula: Future annual healthcare cost = current annual cost × (1+inflation)^years
- [FIRE Calculator](https://freecalculatorsonline.com/calculators/fire-calculator): Estimate a financial-independence target and years to reach it. Formula: FIRE target = annual spending ÷ withdrawal rate; years to target iterate savings and growth
- [Lean FIRE Calculator](https://freecalculatorsonline.com/calculators/lean-fire-calculator): Estimate a target from a lean annual spending plan. Formula: FIRE target = annual spending ÷ withdrawal rate; years to target iterate savings and growth
- [Fat FIRE Calculator](https://freecalculatorsonline.com/calculators/fat-fire-calculator): Estimate a target from a higher retirement spending plan. Formula: FIRE target = annual spending ÷ withdrawal rate; years to target iterate savings and growth
- [Coast FIRE Calculator](https://freecalculatorsonline.com/calculators/coast-fire-calculator): Estimate the invested amount needed today to grow to a future target without new contributions. Formula: Coast FIRE amount = retirement target ÷ (1+return)^years
- [Retirement Income Tax Calculator](https://freecalculatorsonline.com/calculators/retirement-income-tax-calculator): Estimate spendable income from taxable, tax-free and fixed retirement income. Formula: Net retirement income = taxable withdrawals after tax + tax-free withdrawals + fixed income
- [Retirement Monte Carlo Calculator](https://freecalculatorsonline.com/calculators/retirement-monte-carlo-calculator): Stress-test a retirement withdrawal plan across 101 deterministic return paths. Formula: Run 101 deterministic return paths around the entered return and volatility; success means the portfolio remains above zero
- [Sequence of Returns Risk Calculator](https://freecalculatorsonline.com/calculators/sequence-of-returns-risk-calculator): Compare an identical market loss early versus late in a retirement withdrawal horizon. Formula: Compare the same one-time loss at the beginning and end of a withdrawal horizon
- [72(t) SEPP Calculator](https://freecalculatorsonline.com/calculators/72t-sepp-calculator): Estimate annual substantially equal periodic payments using two simplified methods. Formula: RMD-method payment = account balance ÷ life-expectancy factor; amortization-method estimate uses entered rate and factor years
- [Mega Backdoor Roth Capacity Calculator](https://freecalculatorsonline.com/calculators/mega-backdoor-roth-calculator): Estimate potential after-tax plan contribution room below an entered overall limit. Formula: Potential after-tax capacity = overall plan limit − employee deferrals − employer contributions
- [Annuity Growth Calculator](https://freecalculatorsonline.com/calculators/annuity-calculator): Project an annuity’s future value from a starting balance and monthly contributions. Formula: Future value = present balance growth + future value of recurring end-of-month deposits
- [Annuity Payout Calculator](https://freecalculatorsonline.com/calculators/annuity-payout-calculator): Estimate a level monthly payout, total payouts and modeled interest component. Formula: Monthly payout = principal × r ÷ (1 − (1+r)⁻ⁿ)
- [Annuity Present Value Calculator](https://freecalculatorsonline.com/calculators/annuity-present-value-calculator): Calculate the present value of a level monthly annuity payment stream. Formula: Present value = payment × [1 − (1+r)⁻ⁿ] ÷ r
- [Immediate Annuity Calculator](https://freecalculatorsonline.com/calculators/immediate-annuity-calculator): Estimate a level payout from an amount annuitized over a selected period. Formula: Monthly payout = principal × r ÷ (1 − (1+r)⁻ⁿ)
- [Social Security Claiming Age Calculator](https://freecalculatorsonline.com/calculators/social-security-claiming-calculator): Compare cumulative benefits from claiming at 62, full retirement age or 70. Formula: Cumulative benefits = monthly benefit × 12 × years received through the comparison age
- [Social Security Spousal Benefit Calculator](https://freecalculatorsonline.com/calculators/social-security-spousal-benefit-calculator): Estimate a potential spousal amount, top-up and combined household benefit. Formula: Potential spousal amount = max(own benefit, worker PIA × entered spousal percentage)
- [Taxable Social Security Benefits Calculator](https://freecalculatorsonline.com/calculators/taxable-social-security-benefits-calculator): Estimate provisional income and the federal taxable share of Social Security benefits. Formula: Taxable Social Security uses provisional income and entered first and second thresholds, capped at 85% of benefits
- [Multi-Year RMD Calculator](https://freecalculatorsonline.com/calculators/multi-year-rmd-calculator): Project first-year and cumulative RMDs with a declining entered factor and balance growth. Formula: Each year RMD = opening balance ÷ entered factor; balance then grows after distribution and factor declines by one
- [First-Year RMD Timing Calculator](https://freecalculatorsonline.com/calculators/first-year-rmd-deadline-calculator): Estimate the income effect of taking a delayed first RMD and second RMD in the same year. Formula: Combined first-year and second-year RMDs estimate the income effect of delaying the first distribution into year two
- [Retirement Withdrawal Order Calculator](https://freecalculatorsonline.com/calculators/retirement-withdrawal-order-calculator): Model taxable-first, tax-deferred-second and Roth-last withdrawals. Formula: Withdraw taxable assets first, then tax-deferred assets after tax, then Roth assets; all balances receive entered growth
- [Required Retirement Contribution Calculator](https://freecalculatorsonline.com/calculators/required-retirement-contribution-calculator): Calculate annual and monthly employee saving needed to reach a retirement target. Formula: Annual contribution solves the future value target after growth of current savings
- [Barista FIRE Calculator](https://freecalculatorsonline.com/calculators/barista-fire-calculator): Estimate the portfolio target after part-time and other dependable income. Formula: Portfolio target = (annual spending − part-time income − other income) ÷ withdrawal rate
- [Pension COLA Calculator](https://freecalculatorsonline.com/calculators/pension-cola-calculator): Project a pension’s final-year payment and cumulative income with an annual COLA. Formula: Future pension = starting pension × (1+COLA)^years; cumulative payments sum the growing annual benefit
- [401(k) Contribution Calculator](https://freecalculatorsonline.com/calculators/401k-contribution-calculator): Calculate employee, employer and unused overall plan contribution capacity. Formula: Employee contribution = compensation × election rate, capped by entered employee limit; total adds employer contribution and respects overall limit
- [403(b) Contribution Calculator](https://freecalculatorsonline.com/calculators/403b-contribution-calculator): Calculate employee, employer and unused overall 403(b) plan capacity. Formula: Employee contribution = compensation × election rate, capped by entered employee limit; total adds employer contribution and respects overall limit
- [Roth IRA Contribution Calculator](https://freecalculatorsonline.com/calculators/roth-ira-contribution-calculator): Project the value, growth and current after-tax cash cost of an eligible Roth IRA contribution. Formula: Future Roth value = contribution × (1+return)^years; qualified modeled value is shown without a withdrawal-tax haircut
- [Traditional IRA Deduction Calculator](https://freecalculatorsonline.com/calculators/traditional-ira-deduction-calculator): Estimate the current tax effect of a fully or partially deductible IRA contribution. Formula: Potential tax savings = deductible IRA contribution × marginal tax rate
- [Inherited IRA 10-Year Distribution Calculator](https://freecalculatorsonline.com/calculators/inherited-ira-10-year-rule-calculator): Estimate a level annual withdrawal across an entered inherited-account distribution window. Formula: Level annual withdrawal amortizes an inherited balance with growth over the entered distribution window
- [Long-Term Care Cost Calculator](https://freecalculatorsonline.com/calculators/long-term-care-cost-calculator): Project first-year and total long-term-care costs after inflation. Formula: Future first-year cost = current monthly cost × 12 × (1+inflation)^years; total care cost grows annually
- [Early Retirement Health Insurance Calculator](https://freecalculatorsonline.com/calculators/early-retirement-health-insurance-calculator): Estimate the healthcare funding bridge between retirement and Medicare eligibility. Formula: Pre-Medicare bridge cost sums growing premiums and out-of-pocket spending until Medicare eligibility

### Savings & Banking (9)

Plan savings goals, reserves, yields, CDs and time to goal.

Category index: https://freecalculatorsonline.com/calculators/category/savings-banking

- [Savings Growth Calculator](https://freecalculatorsonline.com/calculators/savings-growth-calculator): Project account growth from an opening balance and monthly deposits. Formula: Future value of principal plus end-of-month contributions at compound growth
- [Savings Goal Calculator](https://freecalculatorsonline.com/calculators/savings-goal-calculator): Calculate the monthly deposit needed to reach a future balance. Formula: Monthly savings solves the future-value annuity after current savings growth
- [APY Calculator](https://freecalculatorsonline.com/calculators/apy-calculator): Convert a nominal rate and compounding frequency into effective annual yield. Formula: APY = (1 + nominal rate ÷ periods)^periods − 1
- [CD Savings Calculator](https://freecalculatorsonline.com/calculators/cd-calculator): Estimate CD maturity value and interest from rate, term and compounding. Formula: Maturity value = deposit × (1 + rate/periods)^(periods × years)
- [Emergency Fund Calculator](https://freecalculatorsonline.com/calculators/emergency-fund-calculator): Estimate a reserve target from essential expenses and months of coverage. Formula: Target reserve = essential monthly expenses × months of coverage
- [Time to Save Calculator](https://freecalculatorsonline.com/calculators/time-to-save-calculator): Estimate months needed to reach a goal with regular deposits and growth. Formula: Iterate monthly compounding and deposits until the goal is reached
- [Required Interest Rate Calculator](https://freecalculatorsonline.com/calculators/required-interest-rate-calculator): Calculate the annual return a lump sum needs to reach a target. Formula: Required return = (future value ÷ present value)^(1/years) − 1
- [CD Ladder Calculator](https://freecalculatorsonline.com/calculators/cd-ladder-calculator): Divide savings across CD maturity rungs and estimate interest. Formula: Equal ladder allocation = total amount ÷ number of rungs; blended yield is the entered weighted estimate
- [Millionaire Calculator](https://freecalculatorsonline.com/calculators/millionaire-calculator): Estimate years, contributions and growth required to reach a target balance. Formula: Iterate starting balance, monthly contributions and monthly growth until the target is reached

### Debt & Credit (13)

Understand payoff time, interest, utilization and consolidation.

Category index: https://freecalculatorsonline.com/calculators/category/debt-credit

- [Credit Card Payoff Calculator](https://freecalculatorsonline.com/calculators/credit-card-payoff-calculator): Estimate payoff time and interest for a card balance and fixed payment. Formula: Months = −ln(1 − monthly rate × balance ÷ payment) ÷ ln(1 + monthly rate)
- [Credit Card Interest Calculator](https://freecalculatorsonline.com/calculators/credit-card-interest-calculator): Estimate monthly card interest and the share of your payment that reduces principal. Formula: Monthly interest ≈ average daily balance × APR ÷ 12
- [Balance Transfer Calculator](https://freecalculatorsonline.com/calculators/balance-transfer-calculator): Estimate promotional-period balance and savings after transfer fees. Formula: Compare balance after the promotional term, including the transfer fee
- [Debt Consolidation Calculator](https://freecalculatorsonline.com/calculators/debt-consolidation-calculator): Compare a consolidation loan with current weighted debt. Formula: Compare current weighted-interest payoff with a new amortized loan
- [Credit Utilization Calculator](https://freecalculatorsonline.com/calculators/credit-utilization-calculator): Calculate revolving utilization across balances and limits. Formula: Utilization = reported revolving balances ÷ total limits × 100
- [Debt-to-Income Calculator](https://freecalculatorsonline.com/calculators/debt-to-income-calculator): Calculate required monthly debt as a share of gross monthly income. Formula: Debt-to-income = monthly debt payments ÷ gross monthly income × 100
- [Debt-Free Date Calculator](https://freecalculatorsonline.com/calculators/debt-free-date-calculator): Estimate months remaining on fixed-rate debt at a chosen payment. Formula: Months = −ln(1 − r × balance ÷ payment) ÷ ln(1+r)
- [Credit Card Minimum Payment Calculator](https://freecalculatorsonline.com/calculators/credit-card-minimum-payment-calculator): Estimate payoff time when payments follow a percentage-based minimum. Formula: Minimum payment = max(balance × percentage, fixed minimum); payoff iterates interest and payments
- [Credit Card Payment Calculator](https://freecalculatorsonline.com/calculators/credit-card-payment-calculator): Calculate the monthly payment required to clear a balance by a target date. Formula: Required payment = P × r(1+r)ⁿ ÷ ((1+r)ⁿ−1)
- [Debt Payoff Date Calculator](https://freecalculatorsonline.com/calculators/debt-payoff-date-calculator): Calculate the payment required for a chosen payoff horizon. Formula: Required payment = P × r(1+r)ⁿ ÷ ((1+r)ⁿ−1)
- [Debt Snowball vs. Avalanche Calculator](https://freecalculatorsonline.com/calculators/debt-snowball-vs-avalanche-calculator): Simulate highest-rate-first and smallest-balance-first payoff strategies across three debts. Formula: Simulate monthly minimums plus extra payment using highest-rate-first and smallest-balance-first priority
- [Debt Avalanche Calculator](https://freecalculatorsonline.com/calculators/debt-avalanche-calculator): Calculate payoff time and compare interest with a smallest-balance-first strategy. Formula: Simulate monthly minimums plus extra payment using highest-rate-first and smallest-balance-first priority
- [Debt Snowball Calculator](https://freecalculatorsonline.com/calculators/debt-snowball-calculator): Calculate payoff time and compare interest with a highest-rate-first strategy. Formula: Simulate monthly minimums plus extra payment using highest-rate-first and smallest-balance-first priority

### Taxes & Paycheck (21)

Create educational estimates for federal tax and take-home pay.

Category index: https://freecalculatorsonline.com/calculators/category/taxes-paycheck

- [2026 Federal Income Tax Calculator](https://freecalculatorsonline.com/calculators/federal-income-tax-calculator): Estimate 2026 U.S. ordinary income tax using published brackets and deductions. Formula: 2026 ordinary-income brackets applied after the standard deduction
- [Take-Home Pay Calculator](https://freecalculatorsonline.com/calculators/take-home-pay-calculator): Estimate annual and monthly take-home pay after entered deductions. Formula: Take-home pay = gross pay − estimated tax and benefit deductions
- [Self-Employment Tax Calculator](https://freecalculatorsonline.com/calculators/self-employment-tax-calculator): Estimate self-employment tax from net profit and an entered rate. Formula: SE tax estimate = net profit × 92.35% × entered combined rate
- [Capital Gains Tax Calculator](https://freecalculatorsonline.com/calculators/capital-gains-tax-calculator): Estimate taxable gain and tax from proceeds, basis, costs and rate. Formula: Estimated tax = (proceeds − basis − selling costs) × tax rate
- [Sales Tax Calculator](https://freecalculatorsonline.com/calculators/sales-tax-calculator): Calculate sales tax and final price from a pre-tax amount and rate. Formula: Sales tax = pre-tax price × combined sales-tax rate
- [Property Tax Calculator](https://freecalculatorsonline.com/calculators/property-tax-calculator): Estimate annual and monthly property tax from value and local assumptions. Formula: Tax = market value × assessment ratio × property-tax rate
- [Tax-Equivalent Yield Calculator](https://freecalculatorsonline.com/calculators/tax-equivalent-yield-calculator): Convert a tax-exempt yield into a comparable taxable yield. Formula: Tax-equivalent yield = tax-exempt yield ÷ (1 − marginal tax rate)
- [State Income Tax Calculator](https://freecalculatorsonline.com/calculators/state-income-tax-calculator): Estimate state income tax using a state-specific deduction and rate you enter. Formula: Estimated state tax = max(0, income − entered deduction) × entered effective or marginal rate
- [State Retirement Income Tax Calculator](https://freecalculatorsonline.com/calculators/state-retirement-income-tax-calculator): Estimate state tax on Social Security, pension, retirement withdrawals and other income. Formula: Estimated taxable retirement income = pension + other income + entered taxable share of Social Security − exclusion
- [State Estate Tax Calculator](https://freecalculatorsonline.com/calculators/state-estate-tax-calculator): Estimate state estate tax from an entered exemption, deductions and tax rate. Formula: Estimated tax = max(0, transfer value − exemption − deductions) × entered rate
- [Inheritance Tax Calculator](https://freecalculatorsonline.com/calculators/inheritance-tax-calculator): Estimate inheritance tax from the transfer value, applicable exemption and entered rate. Formula: Estimated tax = max(0, transfer value − exemption − deductions) × entered rate
- [Bonus Take-Home Calculator](https://freecalculatorsonline.com/calculators/bonus-tax-calculator): Estimate net bonus and withholding from entered federal, state and payroll rates. Formula: Net bonus = gross bonus × (1 − entered withholding rates)
- [Overtime Pay Calculator](https://freecalculatorsonline.com/calculators/overtime-pay-calculator): Calculate weekly and annual gross pay using regular and overtime hours. Formula: Weekly gross pay = regular hours × rate + overtime hours × rate × overtime multiplier
- [Paycheck Calculator](https://freecalculatorsonline.com/calculators/paycheck-calculator): Estimate gross pay, deductions and net pay for any pay frequency. Formula: Gross pay per period = annual salary ÷ pay periods; net applies entered effective deductions
- [Marriage Tax Penalty or Bonus Calculator](https://freecalculatorsonline.com/calculators/marriage-tax-calculator): Compare a simplified joint federal estimate with two single-filer estimates. Formula: Marriage effect = estimated joint federal tax − estimated tax if each spouse filed as single
- [QBI Deduction Calculator](https://freecalculatorsonline.com/calculators/qbi-deduction-calculator): Estimate a simplified qualified business income deduction and tax effect. Formula: Simplified QBI deduction = lesser of 20% of qualified business income and 20% of taxable income before QBI
- [Tax Withholding Calculator](https://freecalculatorsonline.com/calculators/tax-withholding-calculator): Project full-year withholding and a potential refund or balance due. Formula: Projected refund or balance = year-to-date withholding + remaining withholding − projected tax
- [Tax Refund or Amount Due Calculator](https://freecalculatorsonline.com/calculators/tax-refund-calculator): Compare projected tax with full-year withholding to estimate refund or balance. Formula: Projected refund or balance = year-to-date withholding + remaining withholding − projected tax
- [Federal Estate Tax Calculator](https://freecalculatorsonline.com/calculators/federal-estate-tax-calculator): Estimate taxable estate and federal estate tax using an entered exemption and rate. Formula: Simplified taxable estate = gross estate − debts − deductions − entered exemption; tax applies at entered rate
- [Reverse Sales Tax Calculator](https://freecalculatorsonline.com/calculators/reverse-sales-tax-calculator): Find the price before tax and the tax amount from a total that already includes sales tax. Formula: Price before tax = total ÷ (1 + tax rate); tax = total − price before tax
- [Gross Pay Calculator](https://freecalculatorsonline.com/calculators/gross-pay-calculator): Calculate gross pay per period and per year from an hourly rate, regular hours and overtime. Formula: Gross pay per period = rate × regular hours + rate × overtime multiplier × overtime hours; yearly = pay per period × periods per year

### Auto Finance (17)

Compare vehicle payments, leases, depreciation and running costs.

Category index: https://freecalculatorsonline.com/calculators/category/auto-finance

- [Auto Loan Calculator](https://freecalculatorsonline.com/calculators/auto-loan-calculator): Calculate monthly payment and total interest on a vehicle loan. Formula: Payment = P × [r(1+r)ⁿ] ÷ [(1+r)ⁿ − 1]
- [Auto Affordability Calculator](https://freecalculatorsonline.com/calculators/auto-affordability-calculator): Estimate an affordable amount financed from payment, rate and term. Formula: Affordable principal = payment × [1 − (1+r)⁻ⁿ] ÷ r
- [Auto Lease Calculator](https://freecalculatorsonline.com/calculators/auto-lease-calculator): Estimate a lease payment from capitalized cost, residual and money factor. Formula: Payment = depreciation charge + finance charge, plus tax
- [Lease vs. Buy Calculator](https://freecalculatorsonline.com/calculators/lease-vs-buy-calculator): Compare lease outlay with purchase payments and resale value. Formula: Compare lease outlay with purchase payments less estimated resale value
- [Auto Depreciation Calculator](https://freecalculatorsonline.com/calculators/auto-depreciation-calculator): Estimate future vehicle value at a constant annual depreciation rate. Formula: Future value = purchase price × (1 − annual depreciation rate)^years
- [Auto Refinance Calculator](https://freecalculatorsonline.com/calculators/auto-refinance-calculator): Estimate payment savings and fee break-even from a lower loan rate. Formula: Break-even months = net refinance costs ÷ monthly payment savings
- [Fuel Cost Calculator](https://freecalculatorsonline.com/calculators/fuel-cost-calculator): Estimate monthly and annual fuel spending from miles, economy and price. Formula: Annual fuel cost = annual miles ÷ fuel economy × fuel price
- [Auto Negative Equity Calculator](https://freecalculatorsonline.com/calculators/auto-negative-equity-calculator): Calculate negative equity and a replacement vehicle’s starting financed amount. Formula: Negative equity = loan payoff − trade value; replacement amount financed adds negative equity, taxes and fees less cash down
- [Vehicle Total Cost of Ownership Calculator](https://freecalculatorsonline.com/calculators/vehicle-total-cost-of-ownership-calculator): Combine depreciation, interest, fuel, insurance, maintenance and fees. Formula: Total ownership cost = depreciation + financing interest + fuel + insurance + maintenance + tax and fees
- [Lease Mileage Calculator](https://freecalculatorsonline.com/calculators/lease-mileage-calculator): Calculate total allowed miles, excess miles and expected mileage charges. Formula: Excess-mileage charge = max(0, actual miles − allowed miles) × per-mile charge
- [Lease Money Factor Calculator](https://freecalculatorsonline.com/calculators/lease-money-factor-calculator): Convert a lease money factor to approximate APR and back again. Formula: Approximate APR = money factor × 2400; money factor = APR ÷ 2400
- [Car Sales Tax & Fees Calculator](https://freecalculatorsonline.com/calculators/car-sales-tax-and-fees-calculator): Estimate taxable price, sales tax and drive-out price after trade credit and incentives. Formula: Drive-out price = vehicle price − trade credit − incentives + taxable charges + sales tax + fees
- [EV vs. Gas Fuel Savings Calculator](https://freecalculatorsonline.com/calculators/ev-vs-gas-fuel-savings-calculator): Compare annual gasoline and electricity costs and premium payback. Formula: Annual energy savings = gasoline cost per mile − EV electricity cost per mile, multiplied by annual miles
- [20/4/10 Car Affordability Calculator](https://freecalculatorsonline.com/calculators/20-4-10-car-affordability-calculator): Test 20% down, a four-year payment and a 10% gross-income transportation target. Formula: 20/4/10 planning check compares 20% down, four-year payment and total transportation cost with 10% of gross monthly income
- [Auto Loan Payoff Calculator](https://freecalculatorsonline.com/calculators/auto-loan-payoff-calculator): Reverse-solve auto-loan payoff time, remaining interest and payoff total from a monthly payment. Formula: Months = −ln(1 − monthly rate × principal ÷ payment) ÷ ln(1 + monthly rate)
- [Trade-In Equity Calculator](https://freecalculatorsonline.com/calculators/trade-in-equity-calculator): Calculate trade equity or negative equity and its effect on replacement financing. Formula: Trade equity = trade value − loan payoff; replacement amount financed applies positive equity or rolls negative equity
- [Cash Back vs Low Interest Calculator](https://freecalculatorsonline.com/calculators/cash-back-vs-low-interest-calculator): Compare taking a cash-back rebate with your own loan against the dealer's low promotional rate. Formula: Payment = P × r ÷ (1 − (1 + r)⁻ⁿ), once with the cash back taken off the price at your own rate, once with the full price at the dealer's low rate; compare total cost

### Real Estate Investing (18)

Evaluate rental income, operating performance and leverage.

Category index: https://freecalculatorsonline.com/calculators/category/real-estate

- [Cap Rate Calculator](https://freecalculatorsonline.com/calculators/cap-rate-calculator): Calculate rental capitalization rate from income, vacancy, expenses and value. Formula: Cap rate = net operating income ÷ property value × 100
- [Cash-on-Cash Return Calculator](https://freecalculatorsonline.com/calculators/cash-on-cash-return-calculator): Calculate annual cash flow as a percentage of cash invested. Formula: Cash-on-cash return = annual cash flow ÷ total cash invested × 100
- [Rental Cash Flow Calculator](https://freecalculatorsonline.com/calculators/rental-cash-flow-calculator): Estimate cash flow after vacancy, operating costs and debt service. Formula: Cash flow = collected rent − operating expenses − debt service
- [Net Operating Income Calculator](https://freecalculatorsonline.com/calculators/noi-calculator): Calculate property NOI and operating expense ratio before financing. Formula: NOI = gross income − vacancy loss − operating expenses
- [DSCR Calculator](https://freecalculatorsonline.com/calculators/dscr-calculator): Calculate debt-service coverage and cash flow after loan payments. Formula: DSCR = net operating income ÷ annual debt service
- [Gross Rent Multiplier Calculator](https://freecalculatorsonline.com/calculators/gross-rent-multiplier-calculator): Calculate property price as a multiple of annual gross rent. Formula: Gross rent multiplier = property price ÷ annual gross rent
- [Break-Even Occupancy Calculator](https://freecalculatorsonline.com/calculators/break-even-occupancy-calculator): Calculate occupancy needed to cover operating costs and debt service. Formula: Break-even occupancy = (expenses + debt service) ÷ potential income
- [Rental Property ROI Calculator](https://freecalculatorsonline.com/calculators/rental-property-roi-calculator): Combine cash flow, principal paydown and appreciation relative to cash invested. Formula: Total rental return = annual cash flow + principal paydown + appreciation divided by total cash invested
- [House Flip Calculator](https://freecalculatorsonline.com/calculators/house-flip-calculator): Estimate flip profit, return on cost and a target maximum purchase price. Formula: Flip profit = sale price − purchase − rehab − holding − selling and financing costs
- [BRRRR Calculator](https://freecalculatorsonline.com/calculators/brrrr-calculator): Estimate refinance proceeds, cash left in the deal and post-refinance cash return. Formula: Cash left in deal = acquisition and rehab cash − refinance proceeds; return = stabilized annual cash flow ÷ cash left
- [Rental Property Depreciation Calculator](https://freecalculatorsonline.com/calculators/rental-property-depreciation-calculator): Estimate depreciable basis, annual depreciation and a simplified tax effect. Formula: Annual building depreciation = depreciable building basis ÷ recovery period
- [1031 Exchange Boot Calculator](https://freecalculatorsonline.com/calculators/1031-exchange-boot-calculator): Estimate realized gain, replacement equity and potential taxable boot. Formula: Estimated taxable boot = cash received + debt relief − replacement debt assumed − additional cash invested, limited to realized gain
- [Price per Square Foot Calculator](https://freecalculatorsonline.com/calculators/price-per-square-foot-calculator): Calculate property price per square foot and compare with a benchmark. Formula: Price per square foot = property price ÷ finished square feet
- [Rent Increase Calculator](https://freecalculatorsonline.com/calculators/rent-increase-calculator): Calculate new rent, effective rent and annual revenue change. Formula: New rent = current rent × (1 + increase rate); annual revenue change = monthly change × occupied units × 12
- [Rental Vacancy Loss Calculator](https://freecalculatorsonline.com/calculators/rental-vacancy-loss-calculator): Calculate potential rent, vacancy loss and effective rental income. Formula: Vacancy loss = potential gross rent × vacancy percentage; effective rent subtracts vacancy and concessions
- [Property Management Fee Calculator](https://freecalculatorsonline.com/calculators/property-management-fee-calculator): Estimate management, leasing and fixed fees as a share of rent. Formula: Property-management cost = collected rent × management rate + leasing and fixed fees
- [Rental Yield Calculator](https://freecalculatorsonline.com/calculators/rental-yield-calculator): Calculate gross and net rental yield from price, annual rent and expenses. Formula: Gross yield = annual rent ÷ price × 100; net yield = (annual rent − annual expenses) ÷ price × 100
- [1% Rule Calculator](https://freecalculatorsonline.com/calculators/one-percent-rule-calculator): Check whether a rental's monthly rent reaches 1 percent of its price, and the shortfall if not. Formula: Rent-to-price ratio = monthly rent ÷ purchase price × 100; rent needed at 1 percent = price × 0.01

### Business Finance (62)

Calculate margins, break-even volume, liquidity and runway.

Category index: https://freecalculatorsonline.com/calculators/category/business

- [Gross Margin Calculator](https://freecalculatorsonline.com/calculators/gross-margin-calculator): Calculate gross profit and margin from revenue and cost of goods sold. Formula: Gross margin = (revenue − cost of goods sold) ÷ revenue × 100
- [Markup Calculator](https://freecalculatorsonline.com/calculators/markup-calculator): Calculate markup on cost and gross profit per unit from cost and selling price. Formula: Markup = (selling price − cost) ÷ cost × 100
- [Business Break-Even Calculator](https://freecalculatorsonline.com/calculators/break-even-calculator): Calculate units and revenue needed to cover fixed and variable costs. Formula: Break-even units = fixed costs ÷ unit contribution margin
- [Profit Margin Calculator](https://freecalculatorsonline.com/calculators/profit-margin-calculator): Calculate net profit and margin from revenue and expenses. Formula: Net profit margin = (revenue − expenses) ÷ revenue × 100
- [Working Capital Calculator](https://freecalculatorsonline.com/calculators/working-capital-calculator): Calculate working capital and current ratio from short-term assets and liabilities. Formula: Working capital = current assets − current liabilities
- [Burn Rate & Runway Calculator](https://freecalculatorsonline.com/calculators/burn-rate-calculator): Calculate monthly net cash burn and the estimated months of operating runway remaining. Formula: Runway = available cash ÷ monthly net burn
- [ROAS Calculator](https://freecalculatorsonline.com/calculators/roas-calculator): Calculate return on ad spend and contribution after media cost. Formula: ROAS = attributed revenue ÷ advertising cost
- [Business Loan Payment Calculator](https://freecalculatorsonline.com/calculators/business-loan-payment-calculator): Estimate a fixed-rate business loan payment and total interest. Formula: Level payment = P × r(1+r)ⁿ ÷ ((1+r)ⁿ−1); each period interest = balance × r
- [Quick Ratio Calculator](https://freecalculatorsonline.com/calculators/quick-ratio-calculator): Compare quick assets with current liabilities. Formula: Ratio = numerator ÷ denominator; cushion = numerator − denominator
- [Cash Ratio Calculator](https://freecalculatorsonline.com/calculators/cash-ratio-calculator): Compare cash resources with current liabilities. Formula: Ratio = numerator ÷ denominator; cushion = numerator − denominator
- [Cash Conversion Cycle Calculator](https://freecalculatorsonline.com/calculators/cash-conversion-cycle-calculator): Combine inventory, receivable and payable days into a cash operating cycle. Formula: Cash conversion cycle = inventory days + receivable days − payable days
- [Days Sales Outstanding Calculator](https://freecalculatorsonline.com/calculators/days-sales-outstanding-calculator): Estimate receivable days from annual credit sales and average receivables. Formula: Days sales outstanding = average accounts receivable ÷ annual credit sales × 365
- [Inventory Turnover Calculator](https://freecalculatorsonline.com/calculators/inventory-turnover-calculator): Calculate inventory turns and average days held. Formula: Turnover = annual flow ÷ average balance; days held = 365 ÷ turnover
- [Contribution Margin Calculator](https://freecalculatorsonline.com/calculators/contribution-margin-calculator): Calculate contribution margin and operating profit after fixed costs. Formula: Contribution margin = revenue − variable costs; ratio = contribution ÷ revenue
- [Operating Leverage Calculator](https://freecalculatorsonline.com/calculators/operating-leverage-calculator): Estimate operating-income sensitivity to a sales change. Formula: Degree of operating leverage = contribution margin ÷ operating income
- [EBITDA Multiple Valuation Calculator](https://freecalculatorsonline.com/calculators/ebitda-multiple-valuation-calculator): Estimate enterprise and equity value from EBITDA and a selected multiple. Formula: Enterprise value = selected earnings metric × valuation multiple; equity value subtracts net debt
- [SDE Business Valuation Calculator](https://freecalculatorsonline.com/calculators/sde-business-valuation-calculator): Estimate small-business value from seller’s discretionary earnings and a multiple. Formula: Enterprise value = selected earnings metric × valuation multiple; equity value subtracts net debt
- [Discounted Cash Flow Calculator](https://freecalculatorsonline.com/calculators/discounted-cash-flow-calculator): Estimate enterprise value from growing cash flow and a terminal value. Formula: Value = Σ cash flowₜ/(1+r)ᵗ plus discounted terminal value
- [Ecommerce Profit Calculator](https://freecalculatorsonline.com/calculators/ecommerce-profit-calculator): Estimate profit after product, fulfillment, platform and advertising costs. Formula: Net profit = revenue − product cost − fulfillment − platform and payment fees − advertising
- [Employee Cost Calculator](https://freecalculatorsonline.com/calculators/employee-cost-calculator): Estimate first-year and monthly loaded employee cost. Formula: First-year hiring cost = salary + payroll burden + benefits + recruiting + equipment
- [Payment Processing Fee Calculator](https://freecalculatorsonline.com/calculators/payment-processing-fee-calculator): Estimate percentage and fixed processing fees and net transaction proceeds. Formula: Processing fee = transaction amount × percentage fee + fixed fee; net proceeds = transaction − fee
- [Invoice Late Fee Calculator](https://freecalculatorsonline.com/calculators/invoice-late-fee-calculator): Estimate a late fee and total amount due from an entered monthly and fixed charge. Formula: Late charge = invoice × monthly rate × months late + fixed charge
- [Current Ratio Calculator](https://freecalculatorsonline.com/calculators/current-ratio-calculator): Calculate current ratio, working capital and liability coverage. Formula: Current ratio = current assets ÷ current liabilities; working capital = assets − liabilities
- [EBITDA Margin Calculator](https://freecalculatorsonline.com/calculators/ebitda-margin-calculator): Calculate EBITDA margin and an implied enterprise value at an entered multiple. Formula: EBITDA margin = EBITDA ÷ revenue; enterprise value estimate = EBITDA × selected multiple
- [Gross Profit Calculator](https://freecalculatorsonline.com/calculators/gross-profit-calculator): Calculate gross profit, gross margin and cost of goods sold. Formula: Gross profit = revenue − cost of goods sold; gross margin = gross profit ÷ revenue
- [Return on Assets Calculator](https://freecalculatorsonline.com/calculators/return-on-assets-calculator): Calculate profit as a percentage of average assets. Formula: Return ratio = annual profit ÷ selected capital base
- [Return on Equity Calculator](https://freecalculatorsonline.com/calculators/return-on-equity-calculator): Calculate profit as a percentage of average equity. Formula: Return ratio = annual profit ÷ selected capital base
- [Return on Invested Capital Calculator](https://freecalculatorsonline.com/calculators/return-on-invested-capital-calculator): Calculate operating profit as a percentage of invested capital. Formula: Return ratio = annual profit ÷ selected capital base
- [Accounts Receivable Aging Calculator](https://freecalculatorsonline.com/calculators/accounts-receivable-aging-calculator): Calculate weighted receivable age and the over-60-day balance share. Formula: Weighted average age = Σ receivable bucket amount × bucket midpoint ÷ total receivables
- [Accounts Payable Turnover Calculator](https://freecalculatorsonline.com/calculators/accounts-payable-turnover-calculator): Calculate payables turnover and days payable outstanding. Formula: Payables turnover = annual purchases ÷ average accounts payable; DPO = 365 ÷ turnover
- [Days Payable Outstanding Calculator](https://freecalculatorsonline.com/calculators/days-payable-outstanding-calculator): Calculate average supplier-payment days from purchases and payables. Formula: Payables turnover = annual purchases ÷ average accounts payable; DPO = 365 ÷ turnover
- [Working Capital Requirement Calculator](https://freecalculatorsonline.com/calculators/working-capital-requirement-calculator): Estimate cash tied in the operating cycle after available credit. Formula: Working-capital need = daily operating cost × cash conversion cycle − available operating credit
- [Business DSCR Calculator](https://freecalculatorsonline.com/calculators/business-dscr-calculator): Calculate business debt-service coverage, cushion and debt capacity at a target ratio. Formula: DSCR = cash flow available for debt service ÷ annual debt service; maximum debt service = cash flow ÷ target DSCR
- [Equipment Lease vs. Buy Calculator](https://freecalculatorsonline.com/calculators/equipment-lease-vs-buy-calculator): Compare lease cost with financed purchase cost after residual value. Formula: Compare lease payments with loan payments minus residual equipment value over the same horizon
- [Contractor vs. Employee Cost Calculator](https://freecalculatorsonline.com/calculators/contractor-vs-employee-calculator): Compare contractor fees with salary, benefits, payroll burden and employee overhead. Formula: Compare loaded employee cost with contractor fees for the same annual hours
- [Economic Order Quantity Calculator](https://freecalculatorsonline.com/calculators/economic-order-quantity-calculator): Calculate EOQ, annual order count and modeled ordering-plus-holding cost. Formula: EOQ = √(2 × annual demand × order cost ÷ annual holding cost per unit)
- [Inventory Reorder Point Calculator](https://freecalculatorsonline.com/calculators/reorder-point-calculator): Calculate lead-time demand, safety stock and an inventory reorder point. Formula: Reorder point = average daily demand × lead time + safety stock
- [Inventory Carrying Cost Calculator](https://freecalculatorsonline.com/calculators/inventory-carrying-cost-calculator): Estimate annual and monthly capital, storage and inventory-risk costs. Formula: Annual carrying cost = average inventory value × carrying-rate percentage
- [Target Margin Pricing Calculator](https://freecalculatorsonline.com/calculators/target-price-calculator): Calculate required selling price, contribution and break-even units. Formula: Required price = unit variable cost ÷ (1 − target margin); volume target covers fixed cost at unit contribution
- [Pallet / Box Loading Calculator](https://freecalculatorsonline.com/calculators/pallet-loading-calculator): Estimate boxes per pallet and volume utilization from pallet and box dimensions. Formula: Boxes per layer = floor(pallet length ÷ box length) × floor(pallet width ÷ box width); layers = floor(max height ÷ box height)
- [Straight-Line Depreciation Calculator](https://freecalculatorsonline.com/calculators/straight-line-depreciation-calculator): Calculate yearly and monthly straight-line depreciation from cost, salvage value and useful life. Formula: Annual depreciation = (cost − salvage value) ÷ useful life
- [Double Declining Balance Depreciation Calculator](https://freecalculatorsonline.com/calculators/double-declining-balance-calculator): Calculate depreciation, book value and accumulated depreciation for any year under the double-declining-balance method. Formula: Yearly depreciation = book value at start of year × (2 ÷ useful life), never taking book value below salvage value
- [GDP Calculator](https://freecalculatorsonline.com/calculators/gdp-calculator): Calculate gross domestic product from consumption, investment, government spending, exports and imports. Formula: GDP = consumption + investment + government spending + (exports − imports)
- [Debt-to-Equity and Debt Ratio Calculator](https://freecalculatorsonline.com/calculators/debt-to-equity-calculator): Calculate debt-to-equity, the debt ratio and the equity multiplier from assets and liabilities. Formula: Debt ratio = total liabilities ÷ total assets; debt-to-equity = total liabilities ÷ shareholders' equity; equity multiplier = total assets ÷ equity
- [Interest Coverage Ratio Calculator](https://freecalculatorsonline.com/calculators/interest-coverage-ratio-calculator): Calculate how many times operating income covers interest expense. Formula: Interest coverage = operating income (EBIT) ÷ interest expense
- [Asset Turnover Calculator](https://freecalculatorsonline.com/calculators/asset-turnover-calculator): Calculate revenue earned per dollar of average assets. Formula: Asset turnover = revenue ÷ average total assets; average assets = (beginning + ending) ÷ 2
- [Operating Margin Calculator](https://freecalculatorsonline.com/calculators/operating-margin-calculator): Calculate operating margin, operating income and gross margin from revenue, costs and expenses. Formula: Gross profit = revenue − COGS; operating income = gross profit − operating expenses; operating margin = operating income ÷ revenue
- [Cost of Goods Sold (COGS) Calculator](https://freecalculatorsonline.com/calculators/cogs-calculator): Calculate cost of goods sold from beginning inventory, purchases and ending inventory. Formula: COGS = beginning inventory + purchases − ending inventory
- [DuPont Analysis Calculator](https://freecalculatorsonline.com/calculators/dupont-analysis-calculator): Break return on equity into profit margin, asset turnover and financial leverage. Formula: ROE = net profit margin × asset turnover × equity multiplier = (net income ÷ revenue) × (revenue ÷ assets) × (assets ÷ equity)
- [Employee Turnover Rate Calculator](https://freecalculatorsonline.com/calculators/employee-turnover-rate-calculator): Calculate the turnover rate from separations and the average headcount. Formula: Turnover rate = separations ÷ average headcount × 100; average headcount = (start + end) ÷ 2
- [Net Promoter Score Calculator](https://freecalculatorsonline.com/calculators/net-promoter-score-calculator): Calculate the net promoter score from counts of promoters, passives and detractors. Formula: NPS = % promoters (scores 9 to 10) − % detractors (scores 0 to 6)
- [Marketing Metrics Calculator](https://freecalculatorsonline.com/calculators/marketing-metrics-calculator): Calculate click-through rate, cost per click, cost per thousand impressions and cost per conversion. Formula: CTR = clicks ÷ impressions; CPC = spend ÷ clicks; CPM = spend ÷ impressions × 1,000; cost per acquisition = spend ÷ conversions
- [Profit Goal Calculator](https://freecalculatorsonline.com/calculators/profit-goal-calculator): Calculate the units and revenue needed to reach a profit goal from fixed costs, price and variable cost. Formula: Units needed = (fixed costs + profit goal) ÷ (price − variable cost per unit)
- [Sum-of-the-Years'-Digits Depreciation Calculator](https://freecalculatorsonline.com/calculators/sum-of-years-digits-depreciation-calculator): Calculate depreciation, book value and accumulated depreciation for any year under the sum-of-the-years'-digits method. Formula: Depreciation in year n = (life − n + 1) ÷ [life × (life + 1) ÷ 2] × (cost − salvage)
- [Units of Production Depreciation Calculator](https://freecalculatorsonline.com/calculators/units-of-production-depreciation-calculator): Calculate depreciation from how much an asset is used, rather than how many years have passed. Formula: Depreciation per unit = (cost − salvage) ÷ total expected units; yearly depreciation = units used × depreciation per unit
- [OEE (Overall Equipment Effectiveness) Calculator](https://freecalculatorsonline.com/calculators/oee-calculator): Calculate overall equipment effectiveness from availability, performance and quality. Formula: OEE = availability × performance × quality
- [Takt Time Calculator](https://freecalculatorsonline.com/calculators/takt-time-calculator): Calculate takt time from available production time and customer demand. Formula: Takt time = available production time ÷ customer demand
- [Safety Stock Calculator](https://freecalculatorsonline.com/calculators/safety-stock-calculator): Calculate safety stock and the reorder point from service level, demand variation and lead time. Formula: Safety stock = z × demand standard deviation × √lead time; reorder point = average daily demand × lead time + safety stock
- [Little's Law Calculator](https://freecalculatorsonline.com/calculators/littles-law-calculator): Calculate the average number of items in a system from the arrival rate and the time each spends there. Formula: L = λ × W, the average number in the system equals the arrival rate times the average time each spends in it
- [Conversion Rate Calculator](https://freecalculatorsonline.com/calculators/conversion-rate-calculator): Calculate conversion rate, revenue per visitor and revenue per conversion. Formula: Conversion rate = conversions ÷ visitors × 100; revenue per visitor = revenue ÷ visitors
- [A/B Test Significance Calculator](https://freecalculatorsonline.com/calculators/ab-test-significance-calculator): Test whether the gap between two conversion rates is likely to be real, with the z-score and p-value. Formula: z = (p_B − p_A) ÷ √(p̂(1 − p̂)(1/n_A + 1/n_B)), with p̂ the pooled rate; two-tailed p = 2 × (1 − Φ(|z|))
- [Overhead Rate Calculator](https://freecalculatorsonline.com/calculators/overhead-rate-calculator): Calculate the overhead rate on labor cost and the overhead per labor hour. Formula: Overhead rate = total overhead ÷ direct labor cost × 100; per hour = total overhead ÷ direct labor hours

### Education & Student Loans (17)

Model student debt, college savings and education economics.

Category index: https://freecalculatorsonline.com/calculators/category/education

- [Student Loan Payment Calculator](https://freecalculatorsonline.com/calculators/student-loan-payment-calculator): Calculate payment and interest for a fixed-rate student loan. Formula: Payment = P × [r(1+r)ⁿ] ÷ [(1+r)ⁿ − 1]
- [Student Loan Payoff Calculator](https://freecalculatorsonline.com/calculators/student-loan-payoff-calculator): Estimate student-loan payoff time and remaining interest at a chosen monthly payment. Formula: Months = −ln(1 − r × balance ÷ payment) ÷ ln(1+r)
- [Student Loan Refinance Calculator](https://freecalculatorsonline.com/calculators/student-loan-refinance-calculator): Estimate break-even and savings from a lower refinance rate. Formula: Break-even months = net refinance costs ÷ monthly payment savings
- [529 Plan Growth Calculator](https://freecalculatorsonline.com/calculators/529-growth-calculator): Project college savings from a balance and monthly deposits. Formula: Future value of principal plus end-of-month contributions at compound growth
- [College Savings Goal Calculator](https://freecalculatorsonline.com/calculators/college-savings-goal-calculator): Calculate monthly savings needed for a future education target. Formula: Monthly savings solves the future-value annuity after current savings growth
- [Student Loan Interest Capitalization Calculator](https://freecalculatorsonline.com/calculators/student-loan-capitalization-calculator): Estimate accrued interest and balance after capitalization. Formula: Capitalized balance = principal + accrued simple interest
- [Education ROI Calculator](https://freecalculatorsonline.com/calculators/education-roi-calculator): Estimate simple ROI and payback from education cost and earnings increase. Formula: ROI = (incremental earnings − education cost) ÷ education cost
- [GPA Calculator](https://freecalculatorsonline.com/calculators/gpa-calculator): Calculate unweighted and weighted GPA from a list of course grades and credit hours. Formula: GPA = Σ(grade points × credit hours) ÷ Σ(credit hours)
- [Grade Target Calculator](https://freecalculatorsonline.com/calculators/grade-target-calculator): Calculate the score needed on remaining coursework to reach a target final grade. Formula: Needed score = (target × 100 − current grade × weight so far) ÷ remaining weight
- [College Cost Calculator](https://freecalculatorsonline.com/calculators/college-cost-calculator): Project a multi-year college cost after education inflation. Formula: Future college cost = current annual cost grown to enrollment, then summed across study years
- [Student Budget Calculator](https://freecalculatorsonline.com/calculators/student-budget-calculator): Set a target for one budget category from monthly resources. Formula: Category target = monthly after-tax income × selected percentage; remaining income is income less target
- [529 State Tax Benefit Calculator](https://freecalculatorsonline.com/calculators/529-state-tax-benefit-calculator): Estimate a state deduction or credit benefit from a 529 contribution. Formula: Estimated state tax benefit = deductible contribution × state rate + entered credit
- [Income-Driven Repayment Calculator](https://freecalculatorsonline.com/calculators/income-driven-repayment-calculator): Estimate a monthly federal student-loan payment from discretionary income assumptions. Formula: Estimated income-driven payment = max(0, AGI − protected income) × assessment rate ÷ 12
- [Parent PLUS Loan Calculator](https://freecalculatorsonline.com/calculators/parent-plus-loan-calculator): Estimate payment, total interest and origination fee on Parent PLUS borrowing. Formula: Payment uses standard amortization; total cost adds an entered origination fee
- [PSLF Calculator](https://freecalculatorsonline.com/calculators/pslf-calculator): Project balance, payment count and out-of-pocket payments to a forgiveness point. Formula: Potential PSLF forgiveness = projected balance at qualifying-payment count minus remaining qualifying payments
- [Scholarship Impact Calculator](https://freecalculatorsonline.com/calculators/scholarship-impact-calculator): Calculate annual net cost, gift aid and remaining borrowing need. Formula: Net college cost = published cost − grants − scholarships − family cash contribution
- [Student Loan Consolidation Rate Calculator](https://freecalculatorsonline.com/calculators/student-loan-consolidation-rate-calculator): Calculate a weighted rate and total balance across three student loans. Formula: Weighted consolidation rate = Σ loan balance × rate ÷ total balance, rounded separately under official rules

### Everyday Money (11)

Handle percentages, discounts, pay conversions and inflation.

Category index: https://freecalculatorsonline.com/calculators/category/everyday

- [Percentage Calculator](https://freecalculatorsonline.com/calculators/percentage-calculator): Calculate what percentage one number represents of another. Formula: Percentage = part ÷ whole × 100
- [Percentage Change Calculator](https://freecalculatorsonline.com/calculators/percentage-change-calculator): Calculate absolute and percentage change between two values. Formula: Change = (new value − original value) ÷ original value × 100
- [Discount Calculator](https://freecalculatorsonline.com/calculators/discount-calculator): Calculate sale price, tax and savings from a percentage discount. Formula: Sale price = original price × (1 − discount), then add tax
- [Tip Calculator](https://freecalculatorsonline.com/calculators/tip-calculator): Calculate a tip, the final bill and an even per-person split for a group. Formula: Tip = bill × tip rate; total per person = total ÷ party size
- [Salary to Hourly Calculator](https://freecalculatorsonline.com/calculators/salary-to-hourly-calculator): Convert annual salary into hourly and monthly gross pay. Formula: Hourly rate = annual salary ÷ (weekly hours × working weeks)
- [Pay Raise Calculator](https://freecalculatorsonline.com/calculators/raise-calculator): Calculate new annual pay and monthly increase from a raise. Formula: New pay = current pay × (1 + raise rate)
- [Inflation Calculator](https://freecalculatorsonline.com/calculators/inflation-calculator): Project the future nominal cost and purchasing-power loss of today’s spending. Formula: Future cost = current cost × (1 + inflation rate)^years
- [Real Wage Calculator](https://freecalculatorsonline.com/calculators/real-wage-calculator): Calculate a pay change after inflation. Formula: Real wage change = (1+nominal raise)/(1+inflation) − 1
- [VAT Calculator](https://freecalculatorsonline.com/calculators/vat-calculator): Estimate a VAT amount and tax-inclusive price using an entered local rate. Formula: VAT = net price × VAT rate; tax-inclusive total = net price + VAT
- [Prorated Rent Calculator](https://freecalculatorsonline.com/calculators/prorated-rent-calculator): Calculate rent for a partial month from the monthly rent, the days in the month and the days occupied. Formula: Prorated rent = monthly rent ÷ days in the month × days occupied
- [Unit Price Comparison Calculator](https://freecalculatorsonline.com/calculators/unit-price-comparison-calculator): Compare the unit price of two package sizes and see how much the cheaper one saves. Formula: Unit price = price ÷ quantity; saving = (higher unit price − lower unit price) ÷ higher unit price

### Bonds & Fixed Income (16)

Price bonds, compare yields and measure interest-rate sensitivity.

Category index: https://freecalculatorsonline.com/calculators/category/bonds-fixed-income

- [Bond Price Calculator](https://freecalculatorsonline.com/calculators/bond-price-calculator): Price a plain fixed-rate bond from coupon, yield and maturity. Formula: Bond price = Σ coupon/(1+y)ᵗ + face/(1+y)ⁿ using coupon-frequency periods
- [Yield to Maturity Calculator](https://freecalculatorsonline.com/calculators/yield-to-maturity-calculator): Estimate the yield that discounts a bond’s cash flows to market price. Formula: Yield to maturity is the discount rate that equates the bond cash flows to its market price
- [Bond Current Yield Calculator](https://freecalculatorsonline.com/calculators/current-yield-calculator): Compare annual coupon income with a bond’s market price. Formula: Yield to maturity is the discount rate that equates the bond cash flows to its market price
- [Bond Duration Calculator](https://freecalculatorsonline.com/calculators/bond-duration-calculator): Estimate modified duration and DV01 for a plain fixed-rate bond. Formula: Macaulay duration is the cash-flow-weighted time; modified duration = Macaulay ÷ (1+y/m)
- [DV01 Calculator](https://freecalculatorsonline.com/calculators/dv01-calculator): Estimate dollar price sensitivity to a one-basis-point yield move. Formula: Macaulay duration is the cash-flow-weighted time; modified duration = Macaulay ÷ (1+y/m)
- [Treasury Bill Calculator](https://freecalculatorsonline.com/calculators/treasury-bill-calculator): Calculate investment yield and bank-discount yield for a T-bill. Formula: Discount yield = (face−price)/face × 360/days; investment yield uses price and 365 days
- [Bond Ladder Calculator](https://freecalculatorsonline.com/calculators/bond-ladder-calculator): Divide an investment across ladder rungs and estimate annual interest. Formula: Equal ladder allocation = total amount ÷ number of rungs; blended yield is the entered weighted estimate
- [Muni vs. Taxable Bond Calculator](https://freecalculatorsonline.com/calculators/muni-vs-taxable-bond-calculator): Compare a taxable after-tax yield with a municipal tax-equivalent yield. Formula: After-tax yield = taxable yield × (1−tax rate); tax-equivalent yield = tax-exempt yield ÷ (1−tax rate)
- [Real Yield Calculator](https://freecalculatorsonline.com/calculators/real-yield-calculator): Estimate return after an inflation assumption. Formula: Real yield = (1 + nominal yield) ÷ (1 + inflation) − 1
- [Yield to Call Calculator](https://freecalculatorsonline.com/calculators/yield-to-call-calculator): Estimate yield to call from bond price, coupons, call price and call date. Formula: Yield to call solves price against coupons through the call date plus the call price
- [Bond Convexity Calculator](https://freecalculatorsonline.com/calculators/bond-convexity-calculator): Estimate bond convexity, price and a duration-plus-convexity yield-shock approximation. Formula: Convexity = Σ CFₜ × t(t+1)/(1+y)^(t+2) ÷ price, adjusted for coupon frequency
- [Zero-Coupon Bond Calculator](https://freecalculatorsonline.com/calculators/zero-coupon-bond-calculator): Calculate the purchase price and accretion of a zero-coupon bond. Formula: Zero-coupon price = face value ÷ (1 + yield/frequency)^(frequency × years)
- [Callable Bond Calculator](https://freecalculatorsonline.com/calculators/callable-bond-calculator): Estimate yield to the first call date and the call premium or discount. Formula: Yield to call solves price against coupons through the call date plus the call price
- [Bond Portfolio Duration Calculator](https://freecalculatorsonline.com/calculators/bond-portfolio-duration-calculator): Calculate weighted modified duration and DV01 for a three-bond portfolio. Formula: Portfolio duration = Σ market value × duration ÷ total market value; DV01 = duration × value × 0.0001
- [Bond Coupon Reinvestment Calculator](https://freecalculatorsonline.com/calculators/coupon-reinvestment-calculator): Project coupon income and reinvestment growth through maturity. Formula: Future value of coupons assumes each coupon is reinvested at the entered rate until maturity
- [TIPS Inflation Adjustment Calculator](https://freecalculatorsonline.com/calculators/tips-calculator): Estimate inflation-adjusted TIPS principal and final-year coupon. Formula: Inflation-adjusted principal = original principal × (1+inflation)^years; coupon uses adjusted principal

### Freelance & Self-Employed (13)

Price independent work, plan taxes and replace employee benefits.

Category index: https://freecalculatorsonline.com/calculators/category/freelance

- [W-2 vs. 1099 Calculator](https://freecalculatorsonline.com/calculators/w2-vs-1099-calculator): Compare employee compensation with contractor revenue after expenses and extra tax. Formula: Compare employee cash compensation and benefits with contractor revenue less overhead and extra taxes
- [Freelance Hourly Rate Calculator](https://freecalculatorsonline.com/calculators/freelance-hourly-rate-calculator): Calculate an hourly rate that covers compensation, benefits, overhead and taxes. Formula: Required hourly rate = target compensation plus benefits, taxes, overhead and profit ÷ billable hours
- [Contractor Rate Calculator](https://freecalculatorsonline.com/calculators/contractor-rate-calculator): Translate a salary target into a sustainable contractor rate. Formula: Required hourly rate = target compensation plus benefits, taxes, overhead and profit ÷ billable hours
- [Billable Hours Calculator](https://freecalculatorsonline.com/calculators/billable-hours-calculator): Calculate billable hours and utilization required for a revenue target. Formula: Required billable hours = revenue target ÷ hourly rate; utilization = billable ÷ available work hours
- [Project Profitability Calculator](https://freecalculatorsonline.com/calculators/project-profitability-calculator): Estimate project profit and margin after labor and direct expenses. Formula: Project profit = client fee − labor hours × internal hourly cost − direct expenses
- [Quarterly Estimated Tax Calculator](https://freecalculatorsonline.com/calculators/quarterly-tax-calculator): Estimate the payment needed across remaining quarterly installments. Formula: Quarterly payment = projected annual tax less withholding and credits ÷ remaining installments
- [Estimated Tax Safe Harbor Calculator](https://freecalculatorsonline.com/calculators/tax-safe-harbor-calculator): Estimate additional prepayment needed to reach an entered prior-year safe harbor. Formula: Required annual prepayment = prior-year tax × safe-harbor percentage less withholding
- [Home Office Deduction Calculator](https://freecalculatorsonline.com/calculators/home-office-deduction-calculator): Estimate deduction and tax savings from an eligible business-use share. Formula: Estimated tax savings = eligible deduction × marginal tax rate
- [Business Mileage Deduction Calculator](https://freecalculatorsonline.com/calculators/business-mileage-deduction-calculator): Estimate a mileage deduction and possible tax savings. Formula: Mileage deduction = business miles × entered standard mileage rate
- [Freelancer Benefits Gap Calculator](https://freecalculatorsonline.com/calculators/benefits-gap-calculator): Estimate the revenue needed to replace salary, benefits and overhead. Formula: Required hourly rate = target compensation plus benefits, taxes, overhead and profit ÷ billable hours
- [Commission Calculator](https://freecalculatorsonline.com/calculators/commission-calculator): Calculate commission and total compensation from sales, rate and base pay. Formula: Commission = eligible sales × rate; total compensation adds base pay
- [Payment Gross-Up Calculator](https://freecalculatorsonline.com/calculators/payment-gross-up-calculator): Calculate the gross payment needed to deliver a desired net amount. Formula: Gross amount = desired net ÷ (1−withholding rate)
- [Solo 401(k) Contribution Calculator](https://freecalculatorsonline.com/calculators/solo-401k-calculator): Estimate maximum solo 401(k) contribution capacity from self-employment profit and age. Formula: Employee deferral (limit + age catch-up) plus 20% employer contribution on net earnings after half of self-employment tax, capped at the combined 2026 limit plus catch-up

### Startup & SaaS (14)

Model recurring revenue, retention, acquisition economics and ownership dilution.

Category index: https://freecalculatorsonline.com/calculators/category/startup-saas

- [MRR & ARR Calculator](https://freecalculatorsonline.com/calculators/mrr-arr-calculator): Calculate ending monthly recurring revenue and annual recurring revenue. Formula: MRR = recurring monthly revenue; ARR = MRR × 12
- [Net Revenue Retention Calculator](https://freecalculatorsonline.com/calculators/net-revenue-retention-calculator): Calculate NRR and GRR from expansion, contraction and churn. Formula: Net retention = (starting recurring revenue + expansion − contraction − churn) ÷ starting revenue
- [LTV:CAC Calculator](https://freecalculatorsonline.com/calculators/customer-ltv-cac-calculator): Estimate customer lifetime value and the LTV-to-CAC ratio. Formula: Customer LTV = ARPU × gross margin ÷ monthly churn; ratio = LTV ÷ CAC
- [CAC Payback Calculator](https://freecalculatorsonline.com/calculators/cac-payback-calculator): Estimate how many months of customer gross profit recover acquisition cost. Formula: CAC payback months = customer acquisition cost ÷ monthly gross profit per customer
- [SaaS Churn Calculator](https://freecalculatorsonline.com/calculators/saas-churn-calculator): Calculate monthly customer churn and a simple implied customer lifetime. Formula: Customer churn = customers lost ÷ starting customers; simple implied lifetime = 1 ÷ monthly churn
- [Pre-Money & Post-Money Valuation Calculator](https://freecalculatorsonline.com/calculators/pre-money-post-money-calculator): Calculate investor and existing-holder ownership after a priced round. Formula: Post-money ownership = investment ÷ post-money valuation; founder ownership is diluted by new ownership
- [Startup Dilution Calculator](https://freecalculatorsonline.com/calculators/startup-dilution-calculator): Estimate ownership dilution from a new investment round. Formula: Post-money ownership = investment ÷ post-money valuation; founder ownership is diluted by new ownership
- [SAFE Conversion Calculator](https://freecalculatorsonline.com/calculators/safe-conversion-calculator): Estimate conversion valuation and ownership from a SAFE cap or discount. Formula: Effective SAFE conversion valuation = lesser of valuation cap and discounted priced-round valuation; ownership ≈ investment ÷ effective post-money value
- [Convertible Note Calculator](https://freecalculatorsonline.com/calculators/convertible-note-calculator): Estimate accrued note value and conversion ownership under a cap or discount. Formula: Accrued note = principal × (1 + simple annual interest × years); conversion valuation uses the lesser of cap and discounted round valuation
- [MRR Growth Calculator](https://freecalculatorsonline.com/calculators/mrr-growth-calculator): Calculate ending MRR, net new MRR and net growth rate. Formula: MRR growth = (ending MRR − beginning MRR) ÷ beginning MRR; net new MRR includes new, expansion, contraction and churn
- [Gross Revenue Retention Calculator](https://freecalculatorsonline.com/calculators/gross-revenue-retention-calculator): Calculate recurring-revenue retention before expansion. Formula: Gross revenue retention = (starting recurring revenue − contraction − churn) ÷ starting recurring revenue
- [SaaS Rule of 40 Calculator](https://freecalculatorsonline.com/calculators/saas-rule-of-40-calculator): Add annual recurring-revenue growth and profitability margin. Formula: Rule of 40 score = annual recurring-revenue growth rate + profit margin
- [SaaS Magic Number Calculator](https://freecalculatorsonline.com/calculators/saas-magic-number-calculator): Compare annualized net new recurring revenue with prior-quarter sales and marketing spend. Formula: SaaS magic number = current-quarter net new ARR ÷ prior-quarter sales and marketing spend
- [Option Pool Dilution Calculator](https://freecalculatorsonline.com/calculators/option-pool-dilution-calculator): Calculate new pool shares and existing-holder dilution at a target pool percentage. Formula: New option-pool shares are solved so the pool equals the target percentage of post-increase fully diluted shares

### Household & Life (24)

Plan insurance, healthcare, childcare, budgets and major life transitions.

Category index: https://freecalculatorsonline.com/calculators/category/household-life

- [Stay-at-Home vs. Childcare Calculator](https://freecalculatorsonline.com/calculators/stay-at-home-vs-childcare-calculator): Estimate the annual cash-flow advantage of working after childcare and job costs. Formula: Net work advantage = take-home pay − childcare − commuting − work-related costs
- [Life Insurance Needs Calculator](https://freecalculatorsonline.com/calculators/life-insurance-needs-calculator): Estimate additional life insurance need after assets and existing coverage. Formula: Coverage need = income replacement + debts + education + final costs − liquid assets − existing coverage
- [HSA Tax Savings Calculator](https://freecalculatorsonline.com/calculators/hsa-tax-savings-calculator): Estimate tax savings and net cost of an HSA contribution. Formula: Tax savings = contribution × combined marginal tax rate; net contribution cost is contribution less savings
- [FSA Tax Savings Calculator](https://freecalculatorsonline.com/calculators/fsa-tax-savings-calculator): Estimate tax savings and net cost of an FSA election. Formula: Tax savings = contribution × combined marginal tax rate; net contribution cost is contribution less savings
- [Health Insurance Plan Cost Calculator](https://freecalculatorsonline.com/calculators/health-insurance-plan-comparison-calculator): Estimate expected and worst-case annual health-plan cost. Formula: Expected annual cost = premiums + expected covered spending share, capped at out-of-pocket maximum
- [Emergency Fund Depletion Calculator](https://freecalculatorsonline.com/calculators/emergency-fund-depletion-calculator): Estimate how long a reserve lasts with monthly inflows, outflows and yield. Formula: Months until depletion iterate balance growth, deposits and withdrawals
- [Sinking Fund Calculator](https://freecalculatorsonline.com/calculators/sinking-fund-calculator): Calculate the monthly deposit needed for a known future expense. Formula: Monthly sinking-fund deposit = target shortfall ÷ months, adjusted for monthly yield
- [Net Worth Calculator](https://freecalculatorsonline.com/calculators/net-worth-calculator): Calculate total household assets less mortgage and other liabilities. Formula: Net worth = total assets − total liabilities
- [50/30/20 Budget Calculator](https://freecalculatorsonline.com/calculators/50-30-20-budget-calculator): Calculate a target amount for a selected budget category. Formula: Category target = monthly after-tax income × selected percentage; remaining income is income less target
- [Subscription Cost Calculator](https://freecalculatorsonline.com/calculators/subscription-cost-calculator): Calculate annual subscription spending and its long-term opportunity cost. Formula: Annual subscription cost = monthly charges × 12 + annual charges; future value shows opportunity cost
- [Cost of Living Calculator](https://freecalculatorsonline.com/calculators/cost-of-living-calculator): Estimate the salary needed to preserve purchasing power across two cost indexes. Formula: Equivalent salary = current salary × destination cost index ÷ current cost index
- [Moving Cost Calculator](https://freecalculatorsonline.com/calculators/moving-cost-calculator): Estimate cash needed for transport, deposits, overlap and setup after reimbursements. Formula: Move cash needed = transport + deposits + travel + overlap + setup − reimbursements
- [Job Offer Total Compensation Calculator](https://freecalculatorsonline.com/calculators/job-offer-comparison-calculator): Estimate annual offer value from salary, bonus, equity, benefits and job costs. Formula: Total offer value = salary + bonus + equity annual value + benefits − commute and other costs
- [Severance Runway Calculator](https://freecalculatorsonline.com/calculators/severance-runway-calculator): Estimate months of essential spending covered by net severance and reserves. Formula: Runway = severance plus liquid reserve ÷ monthly essential spending; net severance applies withholding
- [Paid Leave Income Gap Calculator](https://freecalculatorsonline.com/calculators/paid-leave-gap-calculator): Estimate lost take-home pay, leave benefits and the remaining funding gap. Formula: Leave funding gap = lost take-home pay + added costs − paid leave benefits − employer benefits − saved expenses
- [Maternity Leave Calculator](https://freecalculatorsonline.com/calculators/maternity-leave-calculator): Estimate the household funding gap during maternity or parental leave. Formula: Leave funding gap = lost take-home pay + added costs − paid leave benefits − employer benefits − saved expenses
- [Childcare Break-Even Salary Calculator](https://freecalculatorsonline.com/calculators/childcare-break-even-salary-calculator): Calculate the gross salary required to cover childcare and work-related costs. Formula: Break-even gross salary solves after-tax earnings equal to childcare, commuting and work costs
- [Disability Insurance Needs Calculator](https://freecalculatorsonline.com/calculators/disability-insurance-needs-calculator): Estimate the monthly income-replacement gap after employer and other benefits. Formula: Coverage gap = target income replacement − employer disability benefit − other dependable monthly income
- [Wedding Budget Calculator](https://freecalculatorsonline.com/calculators/wedding-budget-calculator): Build a wedding budget with contingency and calculate monthly savings required. Formula: Wedding budget gap = planned category costs + contingency − current savings − future monthly savings
- [Income-Based Shared Expense Calculator](https://freecalculatorsonline.com/calculators/shared-expense-split-calculator): Split a shared monthly expense in proportion to two incomes. Formula: Each person pays the shared expense in proportion to income
- [Roommate Rent Split Calculator](https://freecalculatorsonline.com/calculators/roommate-rent-split-calculator): Split rent using private-room size and an equal common-space allocation. Formula: Allocate base rent by private-room size and split common-area rent equally
- [Savings Rate Calculator](https://freecalculatorsonline.com/calculators/savings-rate-calculator): Calculate savings rate, monthly savings and remaining spending. Formula: Savings rate = monthly savings and investments ÷ monthly take-home income
- [Salary Negotiation Calculator](https://freecalculatorsonline.com/calculators/salary-negotiation-calculator): Calculate first-year compensation change across salary, bonus, equity and benefits. Formula: Total first-year compensation change = salary increase + bonus change + equity change + benefit-value change
- [Unemployment Runway Calculator](https://freecalculatorsonline.com/calculators/unemployment-runway-calculator): Estimate how long cash reserves last after unemployment income and other inflows. Formula: Runway = cash reserve ÷ (essential expenses − unemployment income − other income)

### Body Composition (11)

Estimate BMI, body fat, lean mass and other body-composition measures.

Category index: https://freecalculatorsonline.com/calculators/category/body-composition

- [BMI Calculator](https://freecalculatorsonline.com/calculators/bmi-calculator): Calculate body mass index from height and weight. Formula: BMI = 703 × weight (lb) ÷ height (in)²
- [Body Fat Percentage Calculator](https://freecalculatorsonline.com/calculators/body-fat-percentage-calculator): Estimate body fat percentage and lean mass using the U.S. Navy circumference method. Formula: U.S. Navy method: men use waist and neck. Women add hip. Both use log₁₀ of the circumference differences.
- [Ideal Weight Calculator](https://freecalculatorsonline.com/calculators/ideal-weight-calculator): Estimate a reference body weight from height using the Devine formula. Formula: Devine formula: 50 kg (men) or 45.5 kg (women) + 2.3 kg per inch over 5 feet
- [Lean Body Mass Calculator](https://freecalculatorsonline.com/calculators/lean-body-mass-calculator): Estimate lean body mass and fat mass using the Boer formula. Formula: Boer formula: men 0.407×kg + 0.267×cm − 19.2; women 0.252×kg + 0.473×cm − 48.3
- [Waist-to-Hip Ratio Calculator](https://freecalculatorsonline.com/calculators/waist-to-hip-ratio-calculator): Calculate waist-to-hip and waist-to-height ratio from body measurements. Formula: Waist-to-hip ratio = waist ÷ hip. Waist-to-height ratio = waist ÷ height
- [Body Surface Area Calculator](https://freecalculatorsonline.com/calculators/body-surface-area-calculator): Calculate body surface area using the Mosteller and Du Bois formulas. Formula: Mosteller: BSA = √(height(cm) × weight(kg) ÷ 3600)
- [Pregnancy Weight Gain Calculator](https://freecalculatorsonline.com/calculators/pregnancy-weight-gain-calculator): Estimate recommended total and to-date pregnancy weight gain by pre-pregnancy BMI. Formula: IOM 2009 guidance: total recommended gain by pre-pregnancy BMI category, prorated to the entered week
- [Due Date Calculator](https://freecalculatorsonline.com/calculators/due-date-calculator): Estimate a pregnancy due date and conception date from the first day of the last menstrual period. Formula: Naegele's rule: due date = first day of last period + 280 days; estimated conception ≈ +14 days
- [Conception Date Calculator](https://freecalculatorsonline.com/calculators/conception-date-calculator): Estimate a conception date and the equivalent last-menstrual-period date from a known or estimated due date. Formula: Estimated conception = due date − 266 days; equivalent last-period start = due date − 280 days
- [Healthy Weight Range Calculator](https://freecalculatorsonline.com/calculators/healthy-weight-range-calculator): Find the weight range that corresponds to a BMI of 18.5 to 24.9 at your height. Formula: Weight (lb) = BMI × height (in)² ÷ 703, at BMI 18.5 and BMI 24.9
- [Weight to Reach a Target BMI Calculator](https://freecalculatorsonline.com/calculators/weight-to-target-bmi-calculator): Find the weight that matches a target BMI at your height and how far you are from it. Formula: Target weight (lb) = target BMI × height (in)² ÷ 703; change = current weight − target weight

### Energy & Nutrition (9)

Estimate calorie needs, macronutrient targets and energy expenditure.

Category index: https://freecalculatorsonline.com/calculators/category/energy-nutrition

- [BMR Calculator](https://freecalculatorsonline.com/calculators/bmr-calculator): Calculate basal metabolic rate using the Mifflin-St Jeor equation. Formula: Mifflin-St Jeor: 10×kg + 6.25×cm − 5×age + 5 (men) or −161 (women)
- [TDEE Calculator](https://freecalculatorsonline.com/calculators/tdee-calculator): Calculate total daily energy expenditure from BMR and activity level. Formula: TDEE = BMR × activity multiplier
- [Calorie Goal Calculator](https://freecalculatorsonline.com/calculators/calorie-goal-calculator): Calculate a target daily calorie intake and estimated weekly weight change. Formula: Target calories = TDEE × (1 + goal %). Weekly change ≈ daily surplus/deficit × 7 ÷ 3,500
- [Macronutrient Calculator](https://freecalculatorsonline.com/calculators/macronutrient-calculator): Calculate protein, carbohydrate and fat targets from a calorie goal and diet style. Formula: Grams = (calories × share) ÷ 4 for protein and carbs, ÷ 9 for fat
- [Protein Intake Calculator](https://freecalculatorsonline.com/calculators/protein-intake-calculator): Calculate a daily protein target from body weight and training goal. Formula: Daily protein (g) = weight (lb) × grams-per-pound target
- [Calories Burned Calculator](https://freecalculatorsonline.com/calculators/calories-burned-calculator): Estimate calories burned from activity, duration and body weight using MET values. Formula: Calories = MET × 3.5 × weight (kg) ÷ 200 × minutes
- [Weight Loss Time Calculator](https://freecalculatorsonline.com/calculators/weight-loss-time-calculator): Estimate the weeks needed to reach a goal weight at a steady daily calorie deficit. Formula: Weeks = (current weight − goal weight) × 3,500 kcal ÷ (daily deficit × 7)
- [Carbohydrate Intake Calculator](https://freecalculatorsonline.com/calculators/carbohydrate-intake-calculator): Convert daily calories into a range of grams of carbohydrate using the Dietary Guidelines share of calories. Formula: Grams = daily calories × share of calories ÷ 4, since a gram of carbohydrate supplies about 4 calories; the acceptable range is 45 to 65 percent of calories
- [Fat Intake Calculator](https://freecalculatorsonline.com/calculators/fat-intake-calculator): Convert daily calories into a range of grams of fat, with a ceiling for saturated fat. Formula: Grams = daily calories × share of calories ÷ 9, since a gram of fat supplies about 9 calories; the acceptable range is 20 to 35 percent, with saturated fat under 10 percent

### Fitness & Performance (6)

Estimate training loads, heart-rate zones and pace.

Category index: https://freecalculatorsonline.com/calculators/category/fitness-performance

- [One-Rep Max Calculator](https://freecalculatorsonline.com/calculators/one-rep-max-calculator): Estimate a one-repetition maximum from a completed set using the Epley formula. Formula: Epley: 1RM = weight × (1 + reps ÷ 30)
- [Target Heart Rate Calculator](https://freecalculatorsonline.com/calculators/target-heart-rate-calculator): Calculate a target training heart-rate zone using the Karvonen method. Formula: Karvonen: target = (220 − age − resting HR) × intensity % + resting HR
- [Running Pace Calculator](https://freecalculatorsonline.com/calculators/running-pace-calculator): Calculate pace per mile and speed from distance and time. Formula: Pace = time ÷ distance. Speed = distance ÷ (time ÷ 60)
- [VO2 Max Calculator](https://freecalculatorsonline.com/calculators/vo2-max-calculator): Estimate VO2 max from the distance covered in a 12-minute run using the Cooper test formula. Formula: Cooper 12-minute run test: VO2 max = (distance in meters − 504.9) ÷ 44.73
- [Wilks Score Calculator](https://freecalculatorsonline.com/calculators/wilks-score-calculator): Calculate a Wilks score to compare powerlifting strength across different bodyweights. Formula: Wilks (1994): score = total lifted (kg) × 500 ÷ (a + b·x + c·x² + d·x³ + e·x⁴ + f·x⁵), x = bodyweight (kg)
- [Max Heart Rate Calculator](https://freecalculatorsonline.com/calculators/max-heart-rate-calculator): Estimate maximum heart rate by age with the Tanaka formula and the older 220 minus age rule. Formula: Tanaka: 208 − 0.7 × age; older rule of thumb: 220 − age

### Clinical Estimates (9)

Educational estimates for kidney function and blood alcohol concentration.

Category index: https://freecalculatorsonline.com/calculators/category/clinical-estimates

- [GFR Calculator](https://freecalculatorsonline.com/calculators/gfr-calculator): Estimate kidney function (eGFR) from creatinine, age and sex using the 2021 CKD-EPI equation. Formula: 2021 CKD-EPI creatinine equation (race-free): 142 × min(Scr/κ,1)^α × max(Scr/κ,1)^-1.200 × 0.9938^age × 1.012 (if female)
- [BAC Calculator](https://freecalculatorsonline.com/calculators/bac-calculator): Estimate blood alcohol concentration from drinks, body weight and elapsed time using the Widmark formula. Formula: Widmark: BAC % = alcohol grams ÷ (body weight (g) × r) × 100 − (hours × 0.015)
- [Creatinine Clearance Calculator](https://freecalculatorsonline.com/calculators/creatinine-clearance-calculator): Estimate creatinine clearance from age, weight and serum creatinine using the Cockcroft-Gault equation. Formula: Cockcroft-Gault: CrCl = (140 − age) × weight (kg) ÷ (72 × serum creatinine); × 0.85 if female
- [Ovulation Calculator](https://freecalculatorsonline.com/calculators/ovulation-calculator): Estimate the ovulation date, fertile window and next period from your last period and cycle length. Formula: Ovulation ≈ first day of last period + cycle length − luteal phase length; fertile window opens 5 days earlier
- [Pregnancy Week Calculator](https://freecalculatorsonline.com/calculators/pregnancy-week-calculator): Find how many weeks and days pregnant you are from the first day of your last period. Formula: Gestational age = days since the first day of the last period; weeks = ⌊days ÷ 7⌋; due date = that first day + 280 days
- [Cholesterol (LDL) Calculator](https://freecalculatorsonline.com/calculators/cholesterol-calculator): Estimate LDL, non-HDL cholesterol and the total-to-HDL ratio from a standard lipid panel. Formula: Friedewald LDL = total − HDL − triglycerides ÷ 5 (mg/dL, valid below 400 mg/dL triglycerides); non-HDL = total − HDL; ratio = total ÷ HDL
- [Mean Arterial Pressure Calculator](https://freecalculatorsonline.com/calculators/mean-arterial-pressure-calculator): Calculate mean arterial pressure and pulse pressure from a blood pressure reading. Formula: MAP = diastolic + (systolic − diastolic) ÷ 3; pulse pressure = systolic − diastolic
- [IVF Due Date Calculator](https://freecalculatorsonline.com/calculators/ivf-due-date-calculator): Estimate a due date from an embryo transfer date and the age of the embryo at transfer. Formula: Due date = transfer date + 266 days − embryo age at transfer; gestational age on transfer day = 14 + embryo age
- [Period Calculator](https://freecalculatorsonline.com/calculators/period-calculator): Predict the next three period start dates from the last period and your cycle length. Formula: Next period = first day of last period + cycle length; each following period adds one more cycle length

### Algebra & Arithmetic (21)

Solve equations, simplify fractions and ratios, and work with exponents, roots and logs.

Category index: https://freecalculatorsonline.com/calculators/category/algebra-arithmetic

- [Quadratic Formula Calculator](https://freecalculatorsonline.com/calculators/quadratic-formula-calculator): Solve ax² + bx + c = 0 for both roots. Formula: x = (−b ± √(b²−4ac)) ÷ 2a
- [Fraction Simplifier Calculator](https://freecalculatorsonline.com/calculators/fraction-simplifier-calculator): Reduce a fraction to lowest terms using the greatest common factor. Formula: Simplified fraction = numerator ÷ GCF, denominator ÷ GCF
- [Exponent Calculator](https://freecalculatorsonline.com/calculators/exponent-calculator): Calculate base raised to an exponent, including negative and fractional exponents. Formula: Result = base^exponent
- [Root Calculator](https://freecalculatorsonline.com/calculators/root-calculator): Calculate the nth root of any value, including cube and higher roots. Formula: Result = value^(1 ÷ degree)
- [Logarithm Calculator](https://freecalculatorsonline.com/calculators/logarithm-calculator): Calculate the logarithm of a value in any base. Formula: log_base(value) = ln(value) ÷ ln(base)
- [Ratio Simplifier Calculator](https://freecalculatorsonline.com/calculators/ratio-simplifier-calculator): Reduce a ratio to its lowest whole-number terms. Formula: Simplified ratio = a ÷ GCF : b ÷ GCF
- [Rounding Calculator](https://freecalculatorsonline.com/calculators/rounding-calculator): Round a value to a chosen number of decimal places. Formula: Rounded value = round(value × 10^places) ÷ 10^places
- [Weighted Average Calculator](https://freecalculatorsonline.com/calculators/weighted-average-calculator): Calculate an average where each value counts by a different weight. Formula: Weighted average = Σ(value × weight) ÷ Σ(weight)
- [2x2 Matrix Determinant Calculator](https://freecalculatorsonline.com/calculators/matrix-2x2-determinant-calculator): Calculate the determinant and trace of a 2x2 matrix. Formula: Determinant = ad − bc; trace = a + d
- [3x3 Matrix Determinant Calculator](https://freecalculatorsonline.com/calculators/matrix-3x3-determinant-calculator): Calculate the determinant and trace of a 3x3 matrix using cofactor expansion. Formula: Determinant via cofactor expansion along the first row; trace = a + e + i
- [Scientific Calculator](https://freecalculatorsonline.com/calculators/scientific-calculator): A full scientific keypad for trig, log, exponent, root, factorial and memory calculations. Formula: x^y and √x shown here; the live tool covers trig, log, exponents, roots, factorial and memory
- [Fraction Calculator](https://freecalculatorsonline.com/calculators/fraction-calculator): Add, subtract, multiply or divide two fractions and get the answer in lowest terms plus its decimal value. Formula: a/b ± c/d = (ad ± bc) ÷ bd; a/b × c/d = ac ÷ bd; a/b ÷ c/d = ad ÷ bc; then divide top and bottom by their greatest common divisor
- [Decimal to Fraction Calculator](https://freecalculatorsonline.com/calculators/decimal-to-fraction-calculator): Turn a decimal into the closest fraction under a denominator limit you choose. Formula: Continued-fraction expansion of the decimal, stopped at the largest denominator you allow, with the closing semiconvergent tested
- [Arithmetic Sequence Calculator](https://freecalculatorsonline.com/calculators/arithmetic-sequence-calculator): Find the last term and the sum of an arithmetic sequence from its first term, common difference and length. Formula: nth term = a₁ + (n−1)d; sum of n terms = n × (a₁ + aₙ) ÷ 2
- [Geometric Sequence Calculator](https://freecalculatorsonline.com/calculators/geometric-sequence-calculator): Find the last term and the sum of a geometric sequence from its first term, common ratio and length. Formula: nth term = a₁ × rⁿ⁻¹; sum of n terms = a₁(1 − rⁿ) ÷ (1 − r), or n × a₁ when r = 1
- [Percent Difference Calculator](https://freecalculatorsonline.com/calculators/percent-difference-calculator): Calculate the percent difference between two values, measured against their average. Formula: Percent difference = |a − b| ÷ ((a + b) ÷ 2) × 100
- [Proportion Calculator](https://freecalculatorsonline.com/calculators/proportion-calculator): Solve a proportion a ÷ b = c ÷ x for the unknown value. Formula: a ÷ b = c ÷ x, so x = b × c ÷ a
- [Roman Numeral Calculator](https://freecalculatorsonline.com/calculators/roman-numeral-calculator): Convert a whole number from 1 to 3,999 into a Roman numeral. Formula: Write the number with the symbols I, V, X, L, C, D and M, subtracting where a smaller symbol comes before a larger one (IV = 4, IX = 9, XL = 40, XC = 90, CD = 400, CM = 900)
- [Completing the Square Calculator](https://freecalculatorsonline.com/calculators/completing-the-square-calculator): Rewrite a quadratic in vertex form and find the vertex from its three coefficients. Formula: a x² + b x + c = a (x − h)² + k, with h = −b ÷ (2a) and k = c − b² ÷ (4a)
- [Dot Product Calculator](https://freecalculatorsonline.com/calculators/dot-product-calculator): Calculate the dot product, the angle and the cross product magnitude of two 3D vectors. Formula: A·B = x₁x₂ + y₁y₂ + z₁z₂; angle = arccos(A·B ÷ (|A| |B|)); |A × B| = |A| |B| sin θ
- [Mixed Number to Improper Fraction Calculator](https://freecalculatorsonline.com/calculators/mixed-number-calculator): Convert a mixed number into an improper fraction and a decimal. Formula: Improper numerator = whole × denominator + numerator; decimal = whole + numerator ÷ denominator

### Geometry (30)

Calculate area, volume, surface area and distance for common shapes.

Category index: https://freecalculatorsonline.com/calculators/category/geometry

- [Rectangle Area & Perimeter Calculator](https://freecalculatorsonline.com/calculators/rectangle-area-calculator): Calculate the area and perimeter of a rectangle. Formula: Area = length × width; perimeter = 2(length + width)
- [Circle Area & Circumference Calculator](https://freecalculatorsonline.com/calculators/circle-area-calculator): Calculate the area and circumference of a circle from its radius. Formula: Area = πr²; circumference = 2πr
- [Triangle Area (Heron's Formula) Calculator](https://freecalculatorsonline.com/calculators/triangle-area-calculator): Calculate a triangle's area and perimeter from its three side lengths. Formula: Heron's formula: s = (a+b+c)/2; area = √(s(s−a)(s−b)(s−c))
- [Pythagorean Theorem Calculator](https://freecalculatorsonline.com/calculators/pythagorean-theorem-calculator): Calculate the hypotenuse of a right triangle from its two legs. Formula: Hypotenuse = √(a² + b²)
- [Sphere Volume & Surface Area Calculator](https://freecalculatorsonline.com/calculators/sphere-volume-calculator): Calculate the volume and surface area of a sphere from its radius. Formula: Volume = (4/3)πr³; surface area = 4πr²
- [Cylinder Volume & Surface Area Calculator](https://freecalculatorsonline.com/calculators/cylinder-volume-calculator): Calculate the volume and surface area of a cylinder. Formula: Volume = πr²h; surface area = 2πr² + 2πrh
- [Cone Volume & Surface Area Calculator](https://freecalculatorsonline.com/calculators/cone-volume-calculator): Calculate the volume and total surface area of a cone. Formula: Volume = (1/3)πr²h; total surface area = πr(r + slant height)
- [Distance & Slope Calculator](https://freecalculatorsonline.com/calculators/distance-slope-calculator): Calculate the distance and slope between two points on a plane. Formula: Distance = √((x₂−x₁)² + (y₂−y₁)²); slope = (y₂−y₁) ÷ (x₂−x₁)
- [Trapezoid Area Calculator](https://freecalculatorsonline.com/calculators/trapezoid-area-calculator): Calculate the area and midsegment of a trapezoid from its two parallel bases and its height. Formula: Area = (base₁ + base₂) ÷ 2 × height; midsegment = (base₁ + base₂) ÷ 2
- [Parallelogram Area Calculator](https://freecalculatorsonline.com/calculators/parallelogram-area-calculator): Calculate the area and perimeter of a parallelogram from its base, height and slanted side. Formula: Area = base × perpendicular height; perimeter = 2 × (base + slanted side)
- [Rectangular Prism Volume Calculator](https://freecalculatorsonline.com/calculators/rectangular-prism-calculator): Calculate the volume, surface area and space diagonal of a box from its length, width and height. Formula: Volume = l × w × h; surface area = 2(lw + lh + wh); space diagonal = √(l² + w² + h²)
- [Triangle Third Side Calculator](https://freecalculatorsonline.com/calculators/triangle-side-calculator): Find the third side, area and perimeter of a triangle from two sides and the angle between them. Formula: c² = a² + b² − 2ab·cos(C); area = ½ab·sin(C)
- [Arc Length and Sector Area Calculator](https://freecalculatorsonline.com/calculators/arc-length-sector-calculator): Calculate arc length, sector area and chord length from a circle's radius and central angle. Formula: Arc length = r × θ; sector area = ½r²θ; chord = 2r·sin(θ ÷ 2), with θ in radians
- [Ellipse Area Calculator](https://freecalculatorsonline.com/calculators/ellipse-area-calculator): Calculate the area and approximate perimeter of an ellipse from its two semi-axes. Formula: Area = π × a × b; perimeter ≈ π(a + b)(1 + 3h ÷ (10 + √(4 − 3h))), h = (a − b)² ÷ (a + b)² (Ramanujan)
- [Pyramid Volume Calculator](https://freecalculatorsonline.com/calculators/pyramid-volume-calculator): Calculate the volume and surface area of a rectangular pyramid from its base and height. Formula: Volume = length × width × height ÷ 3; surface area = base + l·√((w ÷ 2)² + h²) + w·√((l ÷ 2)² + h²)
- [Right Triangle Calculator](https://freecalculatorsonline.com/calculators/right-triangle-calculator): Calculate the hypotenuse, both acute angles and the area of a right triangle from its two legs. Formula: c = √(a² + b²); angle A = arctan(a ÷ b); angle B = 90° − A; area = ½ab
- [Aquarium Volume Calculator](https://freecalculatorsonline.com/calculators/aquarium-volume-calculator): Calculate an aquarium's volume in gallons and liters, and the weight of the water it holds. Formula: Gallons = length × width × height ÷ 231 (cubic inches per US gallon); water weight = gallons × 8.34 lb
- [Annulus Area Calculator](https://freecalculatorsonline.com/calculators/annulus-area-calculator): Calculate the area, width and edge length of a ring from its outer and inner radius. Formula: Area = π × (R² − r²); ring width = R − r; combined edge length = 2π × (R + r)
- [Regular Polygon Calculator](https://freecalculatorsonline.com/calculators/regular-polygon-calculator): Calculate the area, perimeter, apothem and interior angle of a regular polygon from its sides and side length. Formula: Area = n × s² ÷ (4 × tan(π ÷ n)); apothem = s ÷ (2 × tan(π ÷ n)); interior angle = (n − 2) × 180° ÷ n
- [Rhombus Area Calculator](https://freecalculatorsonline.com/calculators/rhombus-area-calculator): Calculate the area, side and perimeter of a rhombus from its two diagonals. Formula: Area = d₁ × d₂ ÷ 2; side = √((d₁ ÷ 2)² + (d₂ ÷ 2)²); perimeter = 4 × side
- [Hemisphere Volume Calculator](https://freecalculatorsonline.com/calculators/hemisphere-calculator): Calculate the volume, curved surface and total surface of a hemisphere from its radius. Formula: Volume = ⅔ × π × r³; curved surface = 2 × π × r²; total surface = 3 × π × r²
- [Cone Frustum Calculator](https://freecalculatorsonline.com/calculators/cone-frustum-calculator): Calculate the volume, slant height and surface area of a truncated cone from its two radii and height. Formula: Volume = π × h × (R² + R×r + r²) ÷ 3; slant = √(h² + (R − r)²); total surface = π × (R² + r²) + π × (R + r) × slant
- [Capsule Volume Calculator](https://freecalculatorsonline.com/calculators/capsule-calculator): Calculate the volume and surface area of a capsule from its radius and straight length. Formula: Volume = π × r² × L + 4⁄3 × π × r³; surface area = 2 × π × r × L + 4 × π × r², with L the straight cylinder section
- [Triangular Prism Volume Calculator](https://freecalculatorsonline.com/calculators/triangular-prism-calculator): Calculate the volume of a triangular prism from the triangle's base and height and the prism's length. Formula: Base area = ½ × base × height; volume = base area × length
- [Law of Sines Calculator](https://freecalculatorsonline.com/calculators/law-of-sines-calculator): Find the two unknown sides and the third angle of a triangle from two angles and one side. Formula: a ÷ sin A = b ÷ sin B = c ÷ sin C, with C = 180° − A − B
- [Cube Calculator](https://freecalculatorsonline.com/calculators/cube-calculator): Calculate the volume, surface area, face diagonal and space diagonal of a cube from its side. Formula: Volume = s³; surface area = 6s²; face diagonal = s√2; space diagonal = s√3
- [Equilateral Triangle Calculator](https://freecalculatorsonline.com/calculators/equilateral-triangle-calculator): Calculate the area, height, perimeter and inscribed circle radius of an equilateral triangle from its side. Formula: Area = √3 ÷ 4 × s²; height = √3 ÷ 2 × s; perimeter = 3s; inradius = s ÷ (2√3)
- [Trigonometry Calculator](https://freecalculatorsonline.com/calculators/trigonometry-calculator): Calculate the sine, cosine and tangent of an angle in degrees. Formula: Sine, cosine and tangent of the angle (sin θ, cos θ, tan θ), with degrees converted to radians by × π ÷ 180
- [Golden Ratio Calculator](https://freecalculatorsonline.com/calculators/golden-ratio-calculator): Split a length into the golden ratio from the longer part, the shorter part or the whole. Formula: Longer part = whole ÷ φ; shorter part = longer part ÷ φ; φ = (1 + √5) ÷ 2 ≈ 1.618034
- [Midpoint Calculator](https://freecalculatorsonline.com/calculators/midpoint-calculator): Find the midpoint and the distance between two points on a plane. Formula: Midpoint = ((x₁ + x₂) ÷ 2, (y₁ + y₂) ÷ 2); distance = √((x₂ − x₁)² + (y₂ − y₁)²)

### Statistics & Probability (13)

Calculate averages, spread, combinations, probability and confidence intervals.

Category index: https://freecalculatorsonline.com/calculators/category/statistics-probability

- [Mean & Median Calculator](https://freecalculatorsonline.com/calculators/mean-median-calculator): Calculate the mean and median of six values. Formula: Mean = Σvalues ÷ n; median = middle value of the sorted list
- [Standard Deviation Calculator](https://freecalculatorsonline.com/calculators/standard-deviation-calculator): Calculate population and sample standard deviation for six values. Formula: Population σ = √(Σ(x−mean)²÷n); sample s = √(Σ(x−mean)²÷(n−1))
- [Range & Midrange Calculator](https://freecalculatorsonline.com/calculators/range-midrange-calculator): Calculate the range and midrange of six values. Formula: Range = max − min; midrange = (max + min) ÷ 2
- [Permutation & Combination Calculator](https://freecalculatorsonline.com/calculators/permutation-combination-calculator): Calculate permutations and combinations for choosing r items from n. Formula: ₙPᵣ = n! ÷ (n−r)!; ₙCᵣ = n! ÷ (r!(n−r)!)
- [Simple Probability Calculator](https://freecalculatorsonline.com/calculators/probability-calculator): Calculate the probability and odds of a simple event. Formula: Probability = favorable outcomes ÷ total outcomes × 100
- [Z-Score Calculator](https://freecalculatorsonline.com/calculators/z-score-calculator): Calculate a z-score and its approximate percentile under a normal distribution. Formula: z = (value − mean) ÷ standard deviation
- [Confidence Interval Calculator](https://freecalculatorsonline.com/calculators/confidence-interval-calculator): Calculate a confidence interval around a sample mean. Formula: Margin of error = z × (σ ÷ √n); interval = mean ± margin
- [Sample Size Calculator](https://freecalculatorsonline.com/calculators/sample-size-calculator): Calculate the sample size needed for a target margin of error and confidence level. Formula: n = (z² × p × (1−p)) ÷ marginOfError²
- [Binomial Probability Calculator](https://freecalculatorsonline.com/calculators/binomial-probability-calculator): Calculate the chance of exactly k successes, and of k or fewer, in n independent trials. Formula: P(X = k) = C(n,k) × pᵏ × (1−p)ⁿ⁻ᵏ; P(X ≤ k) = the sum of P(X = j) for j = 0 to k
- [Normal Distribution Probability Calculator](https://freecalculatorsonline.com/calculators/normal-probability-calculator): Calculate the probability that a normally distributed value falls between two limits. Formula: P(a < X < b) = Φ((b − μ) ÷ σ) − Φ((a − μ) ÷ σ), Φ the standard normal cumulative distribution
- [P-Value from Z-Score Calculator](https://freecalculatorsonline.com/calculators/p-value-calculator): Calculate the p-value for a z-score in a left-tailed, right-tailed or two-tailed test. Formula: P(Z ≤ z) = Φ(z); right tail = 1 − Φ(z); two-tailed p = 2 × (1 − Φ(|z|))
- [Expected Value Calculator](https://freecalculatorsonline.com/calculators/expected-value-calculator): Calculate the expected value of a bet or decision from its chance of winning, the amount won and the amount lost. Formula: Expected value = (chance of winning × amount won) − (chance of losing × amount lost)
- [Bayes' Theorem Calculator](https://freecalculatorsonline.com/calculators/bayes-theorem-calculator): Calculate the chance of a condition after a positive or a negative test from prevalence, sensitivity and false positive rate. Formula: P(condition | positive) = sensitivity × prevalence ÷ [sensitivity × prevalence + false positive rate × (1 − prevalence)]

### Number Theory & Precision (9)

Calculate factors, multiples, scientific notation and measurement error.

Category index: https://freecalculatorsonline.com/calculators/category/number-systems

- [GCF & LCM Calculator](https://freecalculatorsonline.com/calculators/gcf-lcm-calculator): Calculate the greatest common factor and least common multiple of two numbers. Formula: GCF via the Euclidean algorithm; LCM = (a × b) ÷ GCF
- [Prime Factorization Calculator](https://freecalculatorsonline.com/calculators/prime-factorization-calculator): Calculate the number of distinct prime factors and the largest prime factor of a value. Formula: Repeated division by the smallest prime that divides the value
- [Scientific Notation Calculator](https://freecalculatorsonline.com/calculators/scientific-notation-calculator): Convert a value into mantissa-and-exponent scientific notation. Formula: value = mantissa × 10^exponent, 1 ≤ |mantissa| < 10
- [Percent Error Calculator](https://freecalculatorsonline.com/calculators/percent-error-calculator): Calculate the percent error between an experimental and a theoretical value. Formula: Percent error = |experimental − theoretical| ÷ |theoretical| × 100
- [Number Base Converter Calculator](https://freecalculatorsonline.com/calculators/number-base-converter-calculator): Convert a decimal number into binary, hexadecimal and octal at the same time. Formula: The same non-negative integer, displayed in base 2, base 16 and base 8
- [Factorial Calculator](https://freecalculatorsonline.com/calculators/factorial-calculator): Calculate n factorial for a whole number up to 170 and count its trailing zeros. Formula: n! = n × (n−1) × … × 2 × 1; trailing zeros = ⌊n÷5⌋ + ⌊n÷25⌋ + ⌊n÷125⌋ + …
- [Modulo Calculator](https://freecalculatorsonline.com/calculators/modulo-calculator): Find the remainder and whole-number quotient when one number is divided by another. Formula: Quotient = ⌊dividend ÷ divisor⌋; remainder = dividend − divisor × quotient
- [Fibonacci Calculator](https://freecalculatorsonline.com/calculators/fibonacci-calculator): Find the nth Fibonacci number, the ratio to the term before it and the sum of the first n terms. Formula: F(n) = F(n−1) + F(n−2), with F(1) = F(2) = 1; the sum of the first n terms = F(n + 2) − 1
- [Prime Number Calculator](https://freecalculatorsonline.com/calculators/prime-number-calculator): Find the smallest prime factor of a number, and the nearest primes above and below it. Formula: Trial division by every integer up to √n finds the smallest factor; the next and previous primes are found the same way

### Date & Time (6)

Calculate age, date differences, day of the week and countdowns.

Category index: https://freecalculatorsonline.com/calculators/category/date-time

- [Age Calculator](https://freecalculatorsonline.com/calculators/age-calculator): Calculate exact age in years and total days lived from a birth date. Formula: Age = full years elapsed between birth date and the reference date
- [Date Difference Calculator](https://freecalculatorsonline.com/calculators/date-difference-calculator): Calculate the number of days and weeks between two dates. Formula: Days between = end date − start date
- [Day of the Week Calculator](https://freecalculatorsonline.com/calculators/day-of-week-calculator): Find what day of the week any date falls on, and its day of the year. Formula: Day of week = (epoch day + 4) mod 7 (Jan 1, 1970 was a Thursday)
- [Day Counter Calculator](https://freecalculatorsonline.com/calculators/day-counter-calculator): Count down the days and weeks until a target date. Formula: Days until = target date − from date
- [Add Days to a Date Calculator](https://freecalculatorsonline.com/calculators/add-days-to-date-calculator): Add or subtract days and weeks from any date and see the resulting date and weekday. Formula: Result date = start date + days + (7 × weeks)
- [Business Days Calculator](https://freecalculatorsonline.com/calculators/business-days-calculator): Count the weekdays between two dates, plus the calendar days and weekend days. Formula: Business days = weekdays (Monday to Friday) from the start date through the end date, both included

### Unit Conversion (19)

Convert length, weight, temperature, volume, speed and tire sizes.

Category index: https://freecalculatorsonline.com/calculators/category/unit-conversion

- [Length Converter Calculator](https://freecalculatorsonline.com/calculators/length-converter): Convert between millimeters, centimeters, meters, kilometers, inches, feet, yards and miles. Formula: Result = value × (from-unit factor ÷ to-unit factor), factors relative to meters
- [Weight Converter Calculator](https://freecalculatorsonline.com/calculators/weight-converter): Convert between grams, kilograms, pounds, ounces, stone and metric tons. Formula: Result = value × (from-unit factor ÷ to-unit factor), factors relative to kilograms
- [Volume Converter Calculator](https://freecalculatorsonline.com/calculators/volume-converter): Convert between milliliters, liters, US gallons, quarts, cups and fluid ounces. Formula: Result = value × (from-unit factor ÷ to-unit factor), factors relative to liters
- [Speed Converter Calculator](https://freecalculatorsonline.com/calculators/speed-converter): Convert between meters per second, km/h, mph and knots. Formula: Result = value × (from-unit factor ÷ to-unit factor), factors relative to meters/second
- [Temperature Converter Calculator](https://freecalculatorsonline.com/calculators/temperature-converter): Convert between Celsius, Fahrenheit and Kelvin. Formula: Convert through Celsius: C = (F−32)×5/9 or K−273.15; then to target unit
- [Tire Size Comparison Calculator](https://freecalculatorsonline.com/calculators/tire-size-calculator): Compare overall diameter between two tire sizes and estimate speedometer error. Formula: Overall diameter (mm) = 2 × (width × aspect ÷ 100) + wheel diameter × 25.4
- [Currency Converter Calculator](https://freecalculatorsonline.com/calculators/currency-converter-calculator): Convert an amount between currencies using a live, dated exchange rate. Formula: Converted amount = amount × exchange rate
- [Area Converter Calculator](https://freecalculatorsonline.com/calculators/area-converter): Convert between square inches, square feet, square yards, square meters, acres, hectares, square kilometers and square miles. Formula: Result = value × (from-unit factor ÷ to-unit factor), factors relative to square meters
- [Time Converter Calculator](https://freecalculatorsonline.com/calculators/time-converter): Convert between seconds, minutes, hours, days, weeks and years. Formula: Result = value × (from-unit factor ÷ to-unit factor), factors relative to seconds
- [Energy Converter Calculator](https://freecalculatorsonline.com/calculators/energy-converter): Convert between joules, kilojoules, kilocalories, watt-hours, kilowatt-hours, BTU and foot-pounds. Formula: Result = value × (from-unit factor ÷ to-unit factor), factors relative to joules
- [Pressure Converter Calculator](https://freecalculatorsonline.com/calculators/pressure-converter): Convert between pascals, kilopascals, bar, PSI, atmospheres, mmHg and inches of mercury. Formula: Result = value × (from-unit factor ÷ to-unit factor), factors relative to pascals
- [Power Converter Calculator](https://freecalculatorsonline.com/calculators/power-converter): Convert between watts, kilowatts, mechanical horsepower, metric horsepower and BTU per hour. Formula: Result = value × (from-unit factor ÷ to-unit factor), factors relative to watts
- [Height Converter Calculator](https://freecalculatorsonline.com/calculators/height-converter-calculator): Convert a height between feet and inches and centimeters in either direction. Formula: cm = (feet × 12 + inches) × 2.54; feet = ⌊cm ÷ 2.54 ÷ 12⌋, inches = the remainder
- [Angle Converter Calculator](https://freecalculatorsonline.com/calculators/angle-converter-calculator): Convert between degrees, radians, gradians, arcminutes, arcseconds and turns. Formula: Result = value × (from-unit factor ÷ to-unit factor), factors relative to degrees
- [Data Rate Converter Calculator](https://freecalculatorsonline.com/calculators/data-rate-converter-calculator): Convert between bits and bytes per second, from bps to gigabytes per second. Formula: Result = value × (from-unit factor ÷ to-unit factor), factors relative to bits per second; 1 byte = 8 bits
- [Force Converter Calculator](https://freecalculatorsonline.com/calculators/force-converter-calculator): Convert between newtons, kilonewtons, pounds-force, kilograms-force, ounces-force and dynes. Formula: Result = value × (from-unit factor ÷ to-unit factor), factors relative to newtons
- [Torque Converter Calculator](https://freecalculatorsonline.com/calculators/torque-converter-calculator): Convert between newton-meters, pound-feet, pound-inches and kilogram-force meters. Formula: Result = value × (from-unit factor ÷ to-unit factor), factors relative to newton-meters
- [Frequency Converter Calculator](https://freecalculatorsonline.com/calculators/frequency-converter-calculator): Convert between hertz, kilohertz, megahertz, gigahertz and revolutions per minute. Formula: Result = value × (from-unit factor ÷ to-unit factor), factors relative to hertz
- [Fuel Economy Converter Calculator](https://freecalculatorsonline.com/calculators/fuel-economy-converter-calculator): Convert between US miles per gallon, imperial miles per gallon, liters per 100 km and kilometers per liter. Formula: Convert through kilometers per liter: 1 US mpg = 0.425144 km/L, 1 imperial mpg = 0.354006 km/L, L/100 km = 100 ÷ (km/L)

### Home & Construction (17)

Estimate material, tile, roofing and square footage for a project.

Category index: https://freecalculatorsonline.com/calculators/category/home-construction

- [Concrete, Gravel & Mulch Calculator](https://freecalculatorsonline.com/calculators/material-volume-calculator): Estimate the volume and bag count needed for concrete, gravel, mulch or topsoil. Formula: Cubic feet = length × width × (depth ÷ 12); cubic yards = cubic feet ÷ 27
- [Tile Flooring Calculator](https://freecalculatorsonline.com/calculators/tile-calculator): Estimate the number of tiles needed for a room, including a waste allowance. Formula: Tiles needed = (room area ÷ tile area) × (1 + waste %)
- [Roofing Calculator](https://freecalculatorsonline.com/calculators/roofing-calculator): Estimate roofing squares needed from footprint and roof pitch. Formula: Roof surface = footprint × pitch multiplier; squares = surface ÷ 100
- [Square Footage Calculator](https://freecalculatorsonline.com/calculators/square-footage-calculator): Calculate area in square feet and square yards from length and width. Formula: Area = length × width
- [Cut-List / Sheet Nesting Calculator](https://freecalculatorsonline.com/calculators/cut-list-sheet-nesting-calculator): Estimate the number of full sheets needed to cut a set of pieces, including a waste allowance. Formula: Sheets = ceil(total piece area × (1 + waste %) ÷ sheet area)
- [Fastener Pilot & Clearance Hole Reference Calculator](https://freecalculatorsonline.com/calculators/fastener-pilot-hole-calculator): Look up the recommended pilot and clearance hole size for a wood screw gauge and wood type. Formula: Pilot and clearance hole diameters from published wood-screw reference tables by gauge and wood hardness
- [Pool Volume Calculator](https://freecalculatorsonline.com/calculators/pool-volume-calculator): Calculate a pool's volume in gallons, cubic feet and liters from its size and average depth. Formula: Gallons = length × width × average depth × 7.48052 (rectangle) or × 5.87486 (round or oval, which is π ÷ 4 of that)
- [Paint Calculator](https://freecalculatorsonline.com/calculators/paint-calculator): Estimate the gallons of paint a room needs from its size, doors, windows and coats. Formula: Wall area = 2 × (length + width) × height − 20 sq ft per door − 15 sq ft per window; gallons = wall area × coats ÷ coverage per gallon
- [Fence Calculator](https://freecalculatorsonline.com/calculators/fence-calculator): Estimate the posts, pickets and rails a fence needs from its length and layout. Formula: Sections = ⌈length ÷ post spacing⌉; posts = sections + 1; pickets = ⌈length × 12 ÷ (picket width + gap)⌉; rails = sections × rails per section
- [Drywall Calculator](https://freecalculatorsonline.com/calculators/drywall-calculator): Estimate how many drywall sheets a room needs from its area, sheet size and waste allowance. Formula: Sheets = ⌈area × (1 + waste) ÷ sheet area⌉
- [Paver Calculator](https://freecalculatorsonline.com/calculators/paver-calculator): Estimate how many pavers cover an area from the paver size and a waste allowance. Formula: Pavers = ⌈area × 144 ÷ (paver length × paver width) × (1 + waste)⌉
- [Wallpaper Calculator](https://freecalculatorsonline.com/calculators/wallpaper-calculator): Estimate the rolls of wallpaper a room needs from its size, openings and waste. Formula: Wall area = 2 × (length + width) × height − openings; rolls = ⌈wall area × (1 + waste) ÷ coverage per roll⌉
- [Carpet Calculator](https://freecalculatorsonline.com/calculators/carpet-calculator): Estimate square yards and roll length of carpet needed for a room. Formula: Area to buy = room length × width × (1 + waste); square yards = area ÷ 9; roll length (ft) = area to buy ÷ roll width
- [Rainwater Harvesting Calculator](https://freecalculatorsonline.com/calculators/rainwater-harvesting-calculator): Estimate the gallons of rainwater a roof can collect from its area and the rainfall. Formula: Gallons = roof area (sq ft) × rainfall (in) × 0.623 × collection efficiency; 0.623 gallons fall on one square foot per inch of rain
- [Cubic Yard Calculator](https://freecalculatorsonline.com/calculators/cubic-yard-calculator): Calculate cubic yards, cubic feet and cubic meters from a length, a width and a depth in feet. Formula: Cubic yards = length × width × height (all in feet) ÷ 27
- [Cubic Feet Calculator](https://freecalculatorsonline.com/calculators/cubic-feet-calculator): Calculate cubic feet, liters and gallons from a length, a width and a height in any common unit. Formula: Cubic feet = length × width × height, after converting each to feet
- [Flooring Calculator](https://freecalculatorsonline.com/calculators/flooring-calculator): Calculate the boxes of flooring needed to cover a room from its size, the box coverage and a waste allowance. Formula: Boxes = ⌈length × width × (1 + waste) ÷ coverage per box⌉

### Science & Electronics (16)

Calculate circuits, density, molarity and voltage drop.

Category index: https://freecalculatorsonline.com/calculators/category/science-electronics

- [Ohm's Law Calculator](https://freecalculatorsonline.com/calculators/ohms-law-calculator): Calculate voltage and power from current and resistance. Formula: V = I × R; P = V × I
- [Density Calculator](https://freecalculatorsonline.com/calculators/density-calculator): Calculate density and specific gravity from mass and volume. Formula: Density = mass ÷ volume
- [Molarity Calculator](https://freecalculatorsonline.com/calculators/molarity-calculator): Calculate the molar concentration of a solution from moles and volume. Formula: Molarity = moles of solute ÷ liters of solution
- [Voltage Drop Calculator](https://freecalculatorsonline.com/calculators/voltage-drop-calculator): Estimate voltage drop and power loss over a wire run. Formula: Voltage drop = current × (resistance per 1000ft ÷ 1000) × distance × 2 (round trip)
- [Dilution Calculator](https://freecalculatorsonline.com/calculators/dilution-calculator): Calculate the stock volume and diluent needed to reach a target concentration. Formula: C₁ × V₁ = C₂ × V₂, so V₁ = C₂ × V₂ ÷ C₁; diluent = V₂ − V₁
- [pH Value Calculator](https://freecalculatorsonline.com/calculators/ph-calculator): Calculate pH and pOH from a hydrogen ion concentration. Formula: pH = −log₁₀[H⁺]; pOH = 14 − pH at 25 °C, with [H⁺] = a × 10⁻ⁿ mol/L
- [Half-Life Calculator](https://freecalculatorsonline.com/calculators/half-life-calculator): Calculate the amount remaining, the share remaining and the decay constant after a given time. Formula: Remaining = initial × (½)^(elapsed ÷ half-life); decay constant λ = ln 2 ÷ half-life
- [Series and Parallel Resistor Calculator](https://freecalculatorsonline.com/calculators/resistor-calculator): Calculate the combined resistance of up to three resistors in series and in parallel. Formula: Series: R = R₁ + R₂ + R₃; parallel: 1 ÷ R = 1 ÷ R₁ + 1 ÷ R₂ + 1 ÷ R₃ (a zero-ohm resistor in parallel is a short circuit, so the result is 0)
- [LED Resistor Calculator](https://freecalculatorsonline.com/calculators/led-resistor-calculator): Calculate the current-limiting resistor for an LED and the next standard E12 value. Formula: R = (supply voltage − LED forward voltage) ÷ LED current; power = current² × R; then round up to the next E12 value
- [Watts to Amps Calculator](https://freecalculatorsonline.com/calculators/watts-to-amps-calculator): Convert watts to amps for a given voltage, power factor and single-phase or three-phase supply. Formula: Amps = watts ÷ (volts × power factor); three-phase amps = watts ÷ (√3 × volts × power factor)
- [Resistor Color Code Calculator](https://freecalculatorsonline.com/calculators/resistor-color-code-calculator): Read a four-band resistor's value and tolerance range from its color bands. Formula: Resistance = (first digit × 10 + second digit) × multiplier; tolerance sets the minimum and maximum
- [Voltage Divider Calculator](https://freecalculatorsonline.com/calculators/voltage-divider-calculator): Calculate the output voltage and current of a two-resistor voltage divider. Formula: Vout = Vin × R2 ÷ (R1 + R2); current = Vin ÷ (R1 + R2)
- [RC Time Constant Calculator](https://freecalculatorsonline.com/calculators/rc-time-constant-calculator): Calculate the time constant, cutoff frequency and settling time of a resistor-capacitor circuit. Formula: Time constant τ = R × C; cutoff frequency = 1 ÷ (2π × R × C); time to reach 99 percent = 4.6 × τ
- [Combined Gas Law Calculator](https://freecalculatorsonline.com/calculators/combined-gas-law-calculator): Find the final volume of a gas after its pressure and temperature change. Formula: P₁ × V₁ ÷ T₁ = P₂ × V₂ ÷ T₂, so V₂ = P₁ × V₁ × T₂ ÷ (T₁ × P₂), with temperatures in kelvin
- [Percent Yield Calculator](https://freecalculatorsonline.com/calculators/percent-yield-calculator): Calculate the percent yield of a reaction from the actual and theoretical yield. Formula: Percent yield = actual yield ÷ theoretical yield × 100
- [PPM Concentration Calculator](https://freecalculatorsonline.com/calculators/ppm-calculator): Convert a mass of solute in a volume of water to parts per million and parts per billion. Formula: ppm = milligrams of solute ÷ liters of solution (for dilute water solutions); ppb = ppm × 1,000

### Weather (5)

Calculate wind chill, heat index and dew point using the official National Weather Service formulas.

Category index: https://freecalculatorsonline.com/calculators/category/weather

- [Wind Chill Calculator](https://freecalculatorsonline.com/calculators/wind-chill-calculator): Calculate the wind chill "feels-like" temperature using the official NWS formula. Formula: NWS: 35.74 + 0.6215T − 35.75W^0.16 + 0.4275T·W^0.16 (T in °F, W in mph)
- [Heat Index Calculator](https://freecalculatorsonline.com/calculators/heat-index-calculator): Calculate the heat index "feels-like" temperature from air temperature and humidity. Formula: NWS Rothfusz regression on temperature (°F) and relative humidity (%)
- [Dew Point Calculator](https://freecalculatorsonline.com/calculators/dew-point-calculator): Calculate dew point and the temperature-dew point spread from temperature and humidity. Formula: Magnus formula on temperature (°F) and relative humidity (%)
- [Heating & Cooling Degree Days Calculator](https://freecalculatorsonline.com/calculators/degree-days-calculator): Calculate heating and cooling degree days from an average daily temperature using the standard 65°F base. Formula: NOAA convention: heating degree days = max(0, 65°F − avg temp); cooling degree days = max(0, avg temp − 65°F)
- [Snow-to-Liquid Ratio Calculator](https://freecalculatorsonline.com/calculators/snow-to-liquid-ratio-calculator): Estimate snowfall from liquid precipitation using an entered snow-to-liquid ratio. Formula: Estimated snowfall = liquid precipitation × snow-to-liquid ratio

### Plumbing (6)

Size pipe, flow, drainage and water heating for common residential plumbing tasks.

Category index: https://freecalculatorsonline.com/calculators/category/plumbing

- [Pipe Volume Calculator](https://freecalculatorsonline.com/calculators/pipe-volume-calculator): Calculate the volume of water held in a pipe run from its diameter and length. Formula: Volume = π × (D ÷ 24)² × L × 7.48052 (D in inches, L in feet)
- [Flow Rate (GPM) Calculator](https://freecalculatorsonline.com/calculators/flow-rate-gpm-calculator): Calculate gallons per minute from pipe diameter and flow velocity. Formula: GPM = 2.448 × diameter² × velocity (diameter in inches, velocity in ft/sec)
- [Drain Slope Calculator](https://freecalculatorsonline.com/calculators/drain-slope-calculator): Calculate the drop needed along a drain run at a chosen slope. Formula: Drop = pipe run length × slope (inches per foot)
- [Drainage Fixture Unit (DFU) Calculator](https://freecalculatorsonline.com/calculators/drainage-fixture-unit-calculator): Total the drainage fixture units for a group of fixtures and estimate the minimum drain size. Formula: Total DFU = toilets×4 + lavatories×1 + showers×2 + dishwashers×2; minimum drain size from published DFU capacity tables
- [Water Heater Sizing Calculator](https://freecalculatorsonline.com/calculators/water-heater-sizing-calculator): Estimate a storage tank size from household size, or a required flow rate for a tankless unit. Formula: Storage size from a household-size guideline; required tankless flow = simultaneous fixtures × average flow rate
- [Pipe Friction & Pressure Loss Calculator](https://freecalculatorsonline.com/calculators/pipe-friction-loss-calculator): Estimate pressure loss along a pipe run using the Hazen-Williams equation. Formula: hf = 0.2083 × (100 ÷ C)^1.852 × Q^1.852 ÷ d^4.8655 (Hazen-Williams, ft of head per 100 ft)

### HVAC (5)

Estimate duct sizing, airflow, equipment tonnage and static pressure for heating and cooling systems.

Category index: https://freecalculatorsonline.com/calculators/category/hvac

- [Duct Sizing Calculator](https://freecalculatorsonline.com/calculators/duct-sizing-calculator): Estimate the round duct diameter needed for an airflow at a target friction rate. Formula: D = (0.109136 × CFM^1.9 ÷ ΔPf)^(1/5.02) (Huebscher round-duct friction equation)
- [CFM / Air Changes Per Hour Calculator](https://freecalculatorsonline.com/calculators/cfm-air-changes-calculator): Calculate required airflow from room volume and a target air-change rate. Formula: CFM = room volume × air changes per hour ÷ 60
- [HVAC BTU/Tonnage Rough Sizing Calculator](https://freecalculatorsonline.com/calculators/hvac-tonnage-calculator): Estimate a rough cooling load and equipment tonnage from square footage and climate zone. Formula: BTU/hr = square footage × climate-zone factor (rough rule-of-thumb, not a Manual J load calculation)
- [Static Pressure Calculator](https://freecalculatorsonline.com/calculators/static-pressure-calculator): Add supply-side and return-side readings to find total external static pressure. Formula: TESP = supply-side static reading + return-side static reading
- [SEER Upgrade Savings Calculator](https://freecalculatorsonline.com/calculators/seer-upgrade-savings-calculator): Estimate annual operating-cost savings from upgrading to a higher-SEER system. Formula: Annual kWh = capacity × full-load hours ÷ (SEER × 1000); cost = kWh × electricity rate

### Electrical Trade (5)

Size conduit, wire, transformers and boxes using standard NEC reference calculations.

Category index: https://freecalculatorsonline.com/calculators/category/electrical-trade

- [Conduit Fill Calculator](https://freecalculatorsonline.com/calculators/conduit-fill-calculator): Calculate conduit fill percentage from conductor and conduit areas. Formula: Fill % = total conductor area ÷ conduit internal area × 100 (NEC Chapter 9 Table 1 caps fill by conductor count)
- [Wire Ampacity Sizing Calculator](https://freecalculatorsonline.com/calculators/wire-ampacity-calculator): Look up a conductor's base ampacity and apply a derating factor. Formula: Derated ampacity = NEC Table 310.16 base ampacity × combined derating factor
- [Transformer Sizing Calculator](https://freecalculatorsonline.com/calculators/transformer-sizing-calculator): Calculate primary and secondary full-load current from a transformer's KVA rating. Formula: I = KVA × 1000 ÷ (V × √3) for three-phase, or KVA × 1000 ÷ V for single-phase
- [Three-Phase Power Calculator](https://freecalculatorsonline.com/calculators/three-phase-power-calculator): Calculate real and apparent power from three-phase voltage, current and power factor. Formula: kW = √3 × V × I × PF ÷ 1000; KVA = √3 × V × I ÷ 1000
- [Electrical Box Fill Calculator](https://freecalculatorsonline.com/calculators/electrical-box-fill-calculator): Calculate required box volume from conductors, devices, grounds and clamps. Formula: Required volume = Σ conductor allowances + devices×2×largest allowance + ground×largest + clamp×largest (NEC 314.16(B))

### Concrete & Masonry (5)

Estimate concrete, rebar, block and footing quantities for common construction projects.

Category index: https://freecalculatorsonline.com/calculators/category/concrete-masonry

- [Concrete Volume & Bag Calculator](https://freecalculatorsonline.com/calculators/concrete-volume-calculator): Calculate concrete volume and the number of bagged-mix bags needed for a slab or footing. Formula: Volume = L × W × (thickness ÷ 12) ÷ 27 cubic yards; bags = volume (cu ft) ÷ bag yield
- [Rebar Calculator](https://freecalculatorsonline.com/calculators/rebar-calculator): Calculate total rebar length and weight for a rectangular reinforcing grid. Formula: Bars each direction from spacing; total linear feet × weight per foot
- [Concrete Block (CMU) Calculator](https://freecalculatorsonline.com/calculators/cmu-block-calculator): Estimate the number of standard 8x16 blocks and mortar bags for a wall. Formula: Blocks = wall area × 1.125 (8×16 nominal face); mortar bags = blocks ÷ 30
- [Mortar Mix Calculator](https://freecalculatorsonline.com/calculators/mortar-mix-calculator): Calculate mortar volume and bags needed for a given number of brick or block units. Formula: Mortar volume = units ÷ 100 × mortar-per-100 units; bags = volume ÷ bag yield
- [Footing Size Calculator](https://freecalculatorsonline.com/calculators/footing-size-calculator): Estimate the minimum footing width from load and allowable soil bearing pressure. Formula: Required width = load per linear foot ÷ allowable soil bearing pressure

### Carpentry (6)

Calculate rafter, stair, framing and decking dimensions for common carpentry projects.

Category index: https://freecalculatorsonline.com/calculators/category/carpentry

- [Rafter Length Calculator](https://freecalculatorsonline.com/calculators/rafter-length-calculator): Calculate common rafter length and roof angle from run and pitch. Formula: Rafter length = √(run² + (run × pitch ÷ 12)²)
- [Stair Stringer Calculator](https://freecalculatorsonline.com/calculators/stair-stringer-calculator): Calculate the number of risers and stringer length from total rise, target riser and tread. Formula: Steps = round(total rise ÷ target riser); stringer length = √(rise² + ((steps−1) × tread)²)
- [Roof Pitch & Angle Calculator](https://freecalculatorsonline.com/calculators/roof-pitch-angle-calculator): Convert a roof pitch (rise per 12) into a slope angle and percent grade. Formula: Angle = atan(pitch ÷ 12); slope % = pitch ÷ 12 × 100
- [Board Feet Calculator](https://freecalculatorsonline.com/calculators/board-feet-calculator): Calculate board feet per board and for a full order from dimensional lumber sizes. Formula: Board feet = thickness (in) × width (in) × length (ft) ÷ 12
- [Joist Span Reference Calculator](https://freecalculatorsonline.com/calculators/joist-span-reference-calculator): Estimate a rough maximum joist span from nominal depth, spacing and a grade adjustment. Formula: Estimated span ≈ depth × 1.5 × spacing factor × grade factor (rule-of-thumb reference, not the AWC/IRC span table)
- [Deck Material Calculator](https://freecalculatorsonline.com/calculators/deck-material-calculator): Estimate decking boards and joist count from deck dimensions and board spacing. Formula: Boards = ceil(width × 12 ÷ (board width + gap)); joists = floor(width × 12 ÷ joist spacing) + 1

### Machining (4)

Calculate feeds, speeds, tap drill sizes and thread engagement for machine shop work.

Category index: https://freecalculatorsonline.com/calculators/category/machining

- [Feeds and Speeds Calculator](https://freecalculatorsonline.com/calculators/feeds-speeds-calculator): Calculate spindle speed and feed rate from surface speed, tool diameter, chip load and flute count. Formula: RPM = SFM × 3.8197 ÷ diameter; feed rate = RPM × chip load × flutes
- [Tap Drill Size Calculator](https://freecalculatorsonline.com/calculators/tap-drill-size-calculator): Calculate the tap drill diameter for a target percent of thread engagement. Formula: Drill diameter = major diameter − (target % ÷ 75) × (0.974 ÷ TPI)
- [Thread Engagement Calculator](https://freecalculatorsonline.com/calculators/thread-engagement-calculator): Calculate percent thread engagement from major diameter, TPI and the actual drilled hole size. Formula: % thread = (major diameter − hole diameter) × TPI × 75 ÷ 0.974
- [Surface Speed Calculator](https://freecalculatorsonline.com/calculators/surface-speed-calculator): Calculate surface speed (SFM) from workpiece diameter and spindle RPM. Formula: SFM = π × diameter × RPM ÷ 12

### Craft & Sewing (6)

Estimate yarn, fabric, binding and pattern-scaling quantities for knitting, crochet and sewing projects.

Category index: https://freecalculatorsonline.com/calculators/category/craft-sewing

- [Yarn Requirement Calculator](https://freecalculatorsonline.com/calculators/yarn-requirement-calculator): Estimate total yardage and skeins needed for a knit or crochet project from its dimensions and gauge. Formula: Stitches = width × length × gauge²; yardage = stitches ÷ 100 × yards per 100 stitches
- [Knitting & Crochet Gauge Calculator](https://freecalculatorsonline.com/calculators/knitting-gauge-calculator): Convert a pattern's stitch count for your own gauge and a target finished width. Formula: Stitches to cast on = target width × your gauge ÷ 4
- [Fabric Yardage Calculator](https://freecalculatorsonline.com/calculators/fabric-yardage-calculator): Estimate fabric yardage needed for a garment from pattern pieces, fabric width and a waste allowance. Formula: Area = pieces × piece length × piece width × (1 + waste %); yardage = area ÷ (fabric width × 36)
- [Quilt Backing & Binding Calculator](https://freecalculatorsonline.com/calculators/quilt-backing-binding-calculator): Estimate backing and binding fabric yardage from quilt dimensions. Formula: Backing pieces two fabric widths when quilt width plus overhang exceeds fabric width; binding = perimeter × 1.1 ÷ usable strip length × strip width
- [Pattern Scaling Calculator](https://freecalculatorsonline.com/calculators/pattern-scaling-calculator): Calculate a photocopier scale percentage and a resized pattern-piece dimension. Formula: Scale factor = your measurement ÷ original measurement; scaled dimension = piece dimension × scale factor
- [Seam Allowance Calculator](https://freecalculatorsonline.com/calculators/seam-allowance-calculator): Calculate the cut size of a patch from its finished size and seam allowance, and total fabric needed. Formula: Cut size = finished size + 2 × seam allowance; total fabric area = cut size² × quantity

### Networking & Technology (7)

Calculate IP subnets, password entropy, file transfer time and digital storage conversions.

Category index: https://freecalculatorsonline.com/calculators/category/networking-tech

- [Subnet Calculator](https://freecalculatorsonline.com/calculators/subnet-calculator): Calculate the network address, broadcast address and usable host count for an IPv4 address and CIDR prefix. Formula: Network = IP AND subnet mask; broadcast = network OR wildcard mask; usable hosts = 2^(32−prefix) − 2 (RFC 4632 CIDR)
- [Password Entropy Calculator](https://freecalculatorsonline.com/calculators/password-entropy-calculator): Estimate a password's entropy in bits and the average time to crack it at a chosen attack speed. Formula: Entropy (bits) = length × log₂(character-pool size); average crack time = pool size^length ÷ (2 × guesses per second)
- [Download Time Calculator](https://freecalculatorsonline.com/calculators/download-time-calculator): Estimate transfer time from a file size and connection speed, in either decimal or binary units. Formula: Time = (file size in bits) ÷ (connection speed in bits per second)
- [Storage Converter Calculator](https://freecalculatorsonline.com/calculators/storage-converter-calculator): Convert between bits, bytes, kilobytes, kibibytes, megabytes, mebibytes and their gigabyte and terabyte equivalents. Formula: Result = value × (from-unit factor ÷ to-unit factor), factors relative to bits
- [Aspect Ratio Calculator](https://freecalculatorsonline.com/calculators/aspect-ratio-calculator): Reduce a width and height to their aspect ratio and find the height at a new width. Formula: Divide width and height by their greatest common divisor; new height = new width × height ÷ width
- [PPI (Pixels Per Inch) Calculator](https://freecalculatorsonline.com/calculators/ppi-calculator): Calculate a screen's pixel density and pixel pitch from its resolution and diagonal size. Formula: PPI = √(width² + height²) ÷ diagonal size in inches; pixel pitch (mm) = 25.4 ÷ PPI
- [Bandwidth and Data Usage Calculator](https://freecalculatorsonline.com/calculators/bandwidth-calculator): Estimate monthly data use from a bitrate and the hours you stream or transfer each day. Formula: Data per month (GB) = bitrate (Mbps) ÷ 8 × 3,600 × hours per day × days ÷ 1,000

### Physics & Mechanics (14)

Work out speed, force, energy, motion, waves and gas behavior from the standard physics formulas.

Category index: https://freecalculatorsonline.com/calculators/category/physics-mechanics

- [Horsepower Calculator](https://freecalculatorsonline.com/calculators/horsepower-calculator): Calculate horsepower and kilowatts from torque and engine speed. Formula: Horsepower = torque (lb-ft) × RPM ÷ 5,252; kilowatts = horsepower × 0.7457
- [Speed, Distance and Time Calculator](https://freecalculatorsonline.com/calculators/speed-distance-time-calculator): Calculate average speed from distance and travel time. Formula: Speed = distance ÷ time; time in hours = hours + minutes ÷ 60
- [Kinetic Energy Calculator](https://freecalculatorsonline.com/calculators/kinetic-energy-calculator): Calculate kinetic energy and momentum from mass and speed. Formula: KE = ½ × mass × speed²; momentum = mass × speed
- [Newton's Second Law Force Calculator](https://freecalculatorsonline.com/calculators/force-calculator): Calculate force in newtons and pounds-force from mass and acceleration. Formula: Force = mass × acceleration (Newton's second law); 1 lbf = 4.448222 N
- [Uniform Acceleration Calculator](https://freecalculatorsonline.com/calculators/uniform-acceleration-calculator): Calculate final speed, distance and average speed under constant acceleration. Formula: v = u + a × t; s = u × t + ½ × a × t²; average speed = s ÷ t
- [Hooke's Law Calculator](https://freecalculatorsonline.com/calculators/hookes-law-calculator): Calculate a spring's force and stored energy from its spring constant and stretch. Formula: Force = k × x; stored elastic energy = ½ × k × x²
- [Ideal Gas Law Calculator](https://freecalculatorsonline.com/calculators/ideal-gas-law-calculator): Calculate the pressure of a gas from its amount, temperature and volume. Formula: P = n × R × T ÷ V, with R = 0.082057 L·atm ÷ (mol·K)
- [Gravitational Potential Energy Calculator](https://freecalculatorsonline.com/calculators/potential-energy-calculator): Calculate the potential energy of a mass raised to a height. Formula: Gravitational potential energy = m × g × h
- [Work and Power Calculator](https://freecalculatorsonline.com/calculators/work-and-power-calculator): Calculate the work done by a force over a distance, and the power if you know the time. Formula: Work = F × d × cos θ; power = work ÷ time; 1 horsepower = 745.7 W
- [Wavelength and Frequency Calculator](https://freecalculatorsonline.com/calculators/wavelength-frequency-calculator): Convert the frequency of a radio or light wave into its wavelength and period. Formula: Wavelength = speed of light ÷ frequency; period = 1 ÷ frequency; c = 299,792,458 m/s
- [Projectile Motion Calculator](https://freecalculatorsonline.com/calculators/projectile-motion-calculator): Calculate the range, maximum height and flight time of a projectile from its launch speed and angle. Formula: Range = v² × sin 2θ ÷ g; maximum height = v² × sin² θ ÷ (2g); flight time = 2v × sin θ ÷ g, on level ground with no air resistance
- [Free Fall Calculator](https://freecalculatorsonline.com/calculators/free-fall-calculator): Calculate the fall time and impact speed of an object dropped from a height. Formula: Fall time = √(2h ÷ g); impact speed = √(2 × g × h), ignoring air resistance
- [Centripetal Force Calculator](https://freecalculatorsonline.com/calculators/centripetal-force-calculator): Calculate the inward force and acceleration needed to move a mass around a curve. Formula: Centripetal acceleration = v² ÷ r; force = m × v² ÷ r
- [Pendulum Period Calculator](https://freecalculatorsonline.com/calculators/pendulum-period-calculator): Calculate the period and frequency of a pendulum from its length. Formula: Period = 2π × √(L ÷ g), for small swings; frequency = 1 ÷ period

### Time & Clock (8)

Work out sleep times, hours worked, time differences, time zones and military time.

Category index: https://freecalculatorsonline.com/calculators/category/time-clock

- [Sleep Calculator](https://freecalculatorsonline.com/calculators/sleep-calculator): Find bedtimes that let you wake at the end of a sleep cycle, from your wake-up time. Formula: Bedtime = wake-up time − (sleep cycles × cycle length) − minutes to fall asleep
- [Time Card Calculator](https://freecalculatorsonline.com/calculators/time-card-calculator): Calculate hours worked and pay for a shift from start time, end time and unpaid break. Formula: Minutes worked = (end time − start time, wrapped past midnight) − unpaid break; pay = hours worked × hourly rate
- [Time Duration Calculator](https://freecalculatorsonline.com/calculators/time-duration-calculator): Calculate the hours and minutes between two times of day, including across midnight. Formula: Duration = end time − start time, adding 24 hours when the end is earlier than the start
- [Add Time Calculator](https://freecalculatorsonline.com/calculators/add-time-calculator): Add hours and minutes to a time of day and see the resulting time and how many days later it falls. Formula: Result = start time + hours × 60 + minutes, wrapped around a 24-hour day
- [Time Zone Calculator](https://freecalculatorsonline.com/calculators/time-zone-calculator): Convert a time between two time zones, with a setting for daylight saving in each. Formula: Local time at the destination = time − (origin offset + origin daylight saving) + (destination offset + destination daylight saving)
- [Military Time Converter Calculator](https://freecalculatorsonline.com/calculators/military-time-converter-calculator): Convert a time between 12-hour AM and PM and 24-hour military time. Formula: 24-hour time = the 12-hour time with 12 hours added to any PM hour; 12 AM is 00 and 12 PM is 12
- [Hours and Minutes to Decimal Calculator](https://freecalculatorsonline.com/calculators/hours-to-decimal-calculator): Convert hours and minutes into decimal hours for a timesheet or an invoice. Formula: Decimal hours = hours + minutes ÷ 60
- [Decimal Hours to Time Calculator](https://freecalculatorsonline.com/calculators/decimal-to-time-calculator): Convert decimal hours into hours and minutes. Formula: Hours = ⌊decimal hours⌋; minutes = (decimal hours − hours) × 60

### Cooking & Kitchen (4)

Scale recipes, compare pan sizes, dial in a coffee ratio and price a serving.

Category index: https://freecalculatorsonline.com/calculators/category/cooking-kitchen

- [Recipe Scaling Calculator](https://freecalculatorsonline.com/calculators/recipe-scaling-calculator): Scale an ingredient amount from the servings in a recipe to the servings you want. Formula: Scale factor = desired servings ÷ original servings; new amount = original amount × scale factor
- [Baking Pan Size Calculator](https://freecalculatorsonline.com/calculators/baking-pan-size-calculator): Compare two pan sizes and find the multiplier that keeps the batter depth the same. Formula: Recipe multiplier = area of the new pan ÷ area of the original pan (rectangle: length × width; round: π ÷ 4 × diameter²)
- [Coffee to Water Ratio Calculator](https://freecalculatorsonline.com/calculators/coffee-ratio-calculator): Calculate grams of ground coffee from the water you are brewing and your chosen ratio. Formula: Coffee (g) = water (g) ÷ ratio; 1 mL of water weighs 1 g
- [Recipe Cost Per Serving Calculator](https://freecalculatorsonline.com/calculators/recipe-cost-per-serving-calculator): Calculate the cost of one serving from total ingredient cost, servings and an overhead allowance. Formula: Cost per serving = total ingredient cost × (1 + overhead) ÷ servings

### Energy & Utilities (8)

Price appliance electricity, EV charging and fuel economy, and size a battery for a load.

Category index: https://freecalculatorsonline.com/calculators/category/energy-utilities

- [Electricity Cost Calculator](https://freecalculatorsonline.com/calculators/electricity-cost-calculator): Calculate the kilowatt-hours and cost of running any appliance from its wattage, hours and your rate. Formula: kWh = watts ÷ 1,000 × hours per day × days; cost = kWh × price per kWh
- [EV Charging Cost Calculator](https://freecalculatorsonline.com/calculators/ev-charging-cost-calculator): Estimate monthly charging cost and cost per mile for an electric vehicle at home rates. Formula: kWh from the wall = miles ÷ 100 × kWh per 100 miles ÷ (1 − charging loss); cost = kWh × price
- [MPG Calculator](https://freecalculatorsonline.com/calculators/mpg-calculator): Calculate miles per gallon, fuel cost per mile and liters per 100 km from a fill-up. Formula: MPG = miles driven ÷ gallons used; cost per mile = gallons × price ÷ miles; L/100 km = 235.215 ÷ MPG
- [Battery Runtime Calculator](https://freecalculatorsonline.com/calculators/battery-runtime-calculator): Estimate how many hours a battery can run a load from its amp-hours, voltage and usable share. Formula: Runtime (hours) = capacity (Ah) × voltage × usable share ÷ load (watts)
- [Solar Panel Output Calculator](https://freecalculatorsonline.com/calculators/solar-panel-output-calculator): Estimate a solar array's daily and yearly energy from panels, wattage, sun hours and losses. Formula: Daily kWh = panels × panel watts ÷ 1,000 × peak sun hours × (1 − system losses)
- [Solar Payback Calculator](https://freecalculatorsonline.com/calculators/solar-payback-calculator): Estimate the payback period and 25-year net savings of a solar system after incentives. Formula: Payback (years) = (system cost × (1 − incentive)) ÷ annual savings; annual savings = annual kWh × price per kWh
- [LED Bulb Savings Calculator](https://freecalculatorsonline.com/calculators/led-savings-calculator): Calculate yearly electricity savings from swapping older bulbs for LEDs. Formula: Annual kWh saved = (old watts − LED watts) ÷ 1,000 × hours per day × 365 × bulbs; savings = kWh saved × price
- [Generator Size Calculator](https://freecalculatorsonline.com/calculators/generator-size-calculator): Estimate the generator wattage needed from running watts and the largest starting surge. Formula: Starting watts needed = running watts of everything on + the largest single starting surge; add 20 percent headroom

### Lawn & Garden (8)

Order mulch, topsoil, gravel, sand, seed and sod, and plan fertilizer and watering for a yard.

Category index: https://freecalculatorsonline.com/calculators/category/lawn-garden

- [Mulch Calculator](https://freecalculatorsonline.com/calculators/mulch-calculator): Calculate the cubic yards and the bags of mulch needed to cover a bed at a chosen depth. Formula: Cubic yards = area × depth (in) ÷ 12 ÷ 27; bags = cubic feet ÷ bag size
- [Topsoil Calculator](https://freecalculatorsonline.com/calculators/topsoil-calculator): Calculate the cubic yards, bags and tons of topsoil needed for a lawn, a garden or a raised bed. Formula: Cubic yards = area × depth (in) ÷ 12 ÷ 27; bags = cubic feet ÷ bag size; tons = cubic yards × weight per cubic yard
- [Gravel Calculator](https://freecalculatorsonline.com/calculators/gravel-calculator): Calculate the cubic yards and tons of gravel needed to cover a path, a driveway or a bed. Formula: Cubic yards = area × depth (in) ÷ 12 ÷ 27; tons = cubic yards × weight per cubic yard
- [Sand Calculator](https://freecalculatorsonline.com/calculators/sand-calculator): Calculate the cubic yards and tons of sand needed under pavers or in a play area. Formula: Cubic yards = area × depth (in) ÷ 12 ÷ 27; tons = cubic yards × weight per cubic yard
- [Grass Seed Calculator](https://freecalculatorsonline.com/calculators/grass-seed-calculator): Calculate the pounds and bags of grass seed needed for a lawn from its area and a seeding rate. Formula: Seed (lb) = area ÷ 1,000 × seeding rate (lb per 1,000 sq ft); bags = pounds ÷ bag size
- [Lawn Fertilizer Calculator](https://freecalculatorsonline.com/calculators/lawn-fertilizer-calculator): Calculate the pounds and bags of fertilizer needed to apply a set amount of nitrogen to a lawn. Formula: Product (lb) = area ÷ 1,000 × nitrogen rate ÷ (nitrogen % ÷ 100); bags = pounds ÷ bag weight
- [Sod Calculator](https://freecalculatorsonline.com/calculators/sod-calculator): Calculate the number of sod rolls needed to cover a lawn, with a waste allowance. Formula: Rolls = ⌈area × (1 + waste) ÷ roll area⌉
- [Lawn Watering Calculator](https://freecalculatorsonline.com/calculators/lawn-watering-calculator): Calculate the gallons and sprinkler minutes needed to give a lawn a chosen depth of water. Formula: Gallons = area × inches of water × 0.623; minutes = gallons ÷ sprinkler flow (gallons per minute)

## Guides (46)

- [How loan payments work](https://freecalculatorsonline.com/guides/how-loan-payments-work): Understand amortization, APR, term length and the difference between a smaller payment and a lower-cost loan.
- [The full monthly cost of a mortgage](https://freecalculatorsonline.com/guides/mortgage-cost-guide): Build a housing estimate that includes principal, interest, taxes, insurance, association dues and upfront cash.
- [Compound interest and investment projections](https://freecalculatorsonline.com/guides/compound-interest-guide): Use future-value estimates responsibly by separating contributions, growth, time and uncertainty.
- [A practical retirement planning framework](https://freecalculatorsonline.com/guides/retirement-planning-framework): Connect spending, fixed income, portfolio withdrawals, saving rate and uncertainty in one repeatable process.
- [How to build a credit card payoff plan](https://freecalculatorsonline.com/guides/credit-card-payoff-strategy): Turn balances, APRs and monthly cash flow into a payoff date while avoiding common promotional-rate traps.
- [How the 2026 federal tax estimate works](https://freecalculatorsonline.com/guides/2026-federal-tax-estimate-guide): Understand progressive brackets, standard deductions and the limits of a simplified federal ordinary-income estimate.
- [How to compare auto financing and leases](https://freecalculatorsonline.com/guides/auto-financing-guide): Compare payment, amount financed, total interest, depreciation, residual value and ownership horizon.
- [Rental property metrics that work together](https://freecalculatorsonline.com/guides/rental-property-metrics-guide): Understand NOI, cap rate, cash-on-cash return, DSCR, GRM and break-even occupancy without mixing their definitions.
- [Essential business finance ratios](https://freecalculatorsonline.com/guides/business-finance-ratios-guide): Use margin, markup, break-even, working capital, current ratio, burn and runway without confusing their purposes.
- [How to read an amortization schedule](https://freecalculatorsonline.com/guides/amortization-schedule-explained): Follow a level-payment loan from opening balance to final payoff and understand why early payments contain more interest.
- [A complete rent-versus-buy decision framework](https://freecalculatorsonline.com/guides/rent-versus-buy-decision-guide): Compare unrecoverable costs, equity, transaction costs, flexibility and holding period without treating rent as wasted money.
- [ARM and interest-only mortgage risk](https://freecalculatorsonline.com/guides/arm-and-interest-only-risk-guide): Understand reset rates, caps, payment shock and the difference between temporary payment relief and permanent affordability.
- [Bond price, yield and duration explained](https://freecalculatorsonline.com/guides/bond-price-yield-duration-guide): Connect coupon cash flows, market price, yield to maturity, duration and DV01 in one fixed-income framework.
- [T-bills, CDs and maturity ladders](https://freecalculatorsonline.com/guides/treasury-bill-and-ladder-guide): Compare short-term yield conventions and design a ladder around liquidity dates , not chasing one headline rate.
- [IRR, time-weighted and annualized return](https://freecalculatorsonline.com/guides/investment-return-measurement-guide): Choose the return measure that matches the question and avoid misleading comparisons across cash-flow patterns.
- [Investment fees and risk metrics](https://freecalculatorsonline.com/guides/investment-fees-risk-metrics-guide): Read expense drag, Sharpe, Sortino and maximum drawdown as complementary measurements , not a single scorecard.
- [RMD and QCD planning](https://freecalculatorsonline.com/guides/rmd-and-qcd-planning-guide): Use prior year-end balances, official life-expectancy factors and charitable distribution rules without turning a planning estimate into tax advice.
- [Roth conversion and bracket planning](https://freecalculatorsonline.com/guides/roth-conversion-planning-guide): Model conversion tax, bracket room, IRA basis and future tax-rate assumptions before moving retirement assets.
- [Social Security claiming and pension choices](https://freecalculatorsonline.com/guides/social-security-pension-guide): Compare break-even age, survivor value, inflation protection and present value without reducing lifetime income to one crossover date.
- [FIRE, Coast FIRE and retirement target variants](https://freecalculatorsonline.com/guides/fire-and-coast-fire-guide): Translate lifestyle spending into Lean, traditional, Fat and Coast FIRE targets while keeping withdrawal-rate uncertainty visible.
- [Freelancer and contractor pricing](https://freecalculatorsonline.com/guides/freelancer-pricing-guide): Replace salary, benefits, taxes, overhead and nonbillable time before setting an hourly or project rate.
- [Quarterly estimated tax and safe harbor](https://freecalculatorsonline.com/guides/estimated-tax-safe-harbor-guide): Separate projected liability from payment-timing protection and update the estimate as self-employment income changes.
- [Working capital and the cash conversion cycle](https://freecalculatorsonline.com/guides/cash-conversion-cycle-guide): Connect inventory days, receivable days, payable days, liquidity ratios and cash forecasting.
- [SaaS revenue, retention and unit economics](https://freecalculatorsonline.com/guides/saas-metrics-guide): Define MRR, ARR, NRR, GRR, churn, LTV and CAC consistently before using them for planning or valuation.
- [Startup valuation and dilution](https://freecalculatorsonline.com/guides/startup-dilution-guide): Connect pre-money value, post-money value, new investor ownership and existing-holder dilution before a financing round.
- [Health plan, HSA and FSA cost comparison](https://freecalculatorsonline.com/guides/health-plan-hsa-guide): Compare premiums, expected care, deductibles, coinsurance, maximum exposure and tax-advantaged accounts.
- [Emergency funds, sinking funds and financial runway](https://freecalculatorsonline.com/guides/household-emergency-plan-guide): Separate known future expenses from true emergencies and use depletion modeling to set action deadlines.
- [How to estimate life insurance need](https://freecalculatorsonline.com/guides/life-insurance-needs-guide): Convert survivor income, debts, education, final expenses, assets and existing coverage into a transparent range.
- [College cost, savings and student debt planning](https://freecalculatorsonline.com/guides/college-cost-and-529-guide): Combine net price, education inflation, 529 growth, aid uncertainty and student-loan terms.
- [How to size a backup generator](https://freecalculatorsonline.com/guides/size-a-backup-generator-guide): Build an essential-load list, separate running watts from starting surge and choose a generator, battery or both without buying too big or too small.
- [Geometry for DIY and design: area, volume and angles](https://freecalculatorsonline.com/guides/geometry-for-diy-guide): Break odd shapes into simple ones, choose the right formula for the shape in front of you and avoid the mistakes that cost material and money.
- [Physics formulas for everyday questions](https://freecalculatorsonline.com/guides/everyday-physics-formulas-guide): Use the standard formulas for speed, force, energy, work, power and projectiles to answer practical questions, and know where the textbook model stops working.
- [What body and nutrition calculators can tell you](https://freecalculatorsonline.com/guides/body-nutrition-calculators-guide): Use BMI, healthy weight ranges, calorie deficits, macronutrient ranges and heart rate estimates as screening tools, and know when to ask a clinician.
- [Fractions, decimals and percentages explained](https://freecalculatorsonline.com/guides/fractions-decimals-percentages-guide): Move between the three ways of writing a part of a whole, add and simplify fractions, and choose the right percent measure for a change or a difference.
- [Electronics basics: Ohm's law, resistors, dividers and LEDs](https://freecalculatorsonline.com/guides/electronics-basics-guide): Use Ohm's law, resistor color codes, voltage dividers, RC circuits and LED resistors to size parts for a simple circuit, and know the limits of the formulas.
- [Lab calculations: dilutions, pH, half-life and yield](https://freecalculatorsonline.com/guides/lab-calculations-guide): Work through common bench and classroom calculations, from diluting a stock solution to converting a trace concentration, and avoid slips that spoil results.
- [Operations metrics: OEE, takt time and safety stock](https://freecalculatorsonline.com/guides/operations-metrics-guide): Measure how well a line runs, set its pace from demand, buffer inventory against uncertainty and size a queue from two numbers you can observe.
- [Marketing metrics: conversion rate, CTR, CPC, CPA and ROAS](https://freecalculatorsonline.com/guides/marketing-metrics-guide): Read an ad campaign or a website through a few ratios, know what each one measures and avoid optimizing the wrong number.
- [How to work out what an appliance costs to run](https://freecalculatorsonline.com/guides/appliance-running-cost-guide): Turn a wattage label, the hours of use and your electricity rate into a monthly and yearly cost, then decide which changes are worth making.
- [Time cards, decimal hours and overtime explained](https://freecalculatorsonline.com/guides/time-cards-decimal-hours-guide): Convert clock times into paid hours, handle breaks and shifts that cross midnight, and check gross pay before a paycheck goes out.
- [How to estimate materials for a home project](https://freecalculatorsonline.com/guides/home-project-materials-guide): Measure a room correctly, subtract openings, add the right waste allowance and round up to what suppliers sell, for paint, drywall, flooring and fencing.
- [Depreciation methods compared](https://freecalculatorsonline.com/guides/depreciation-methods-guide): See how straight-line, double-declining balance, sum-of-the-years'-digits and units-of-production depreciation spread the same cost differently.
- [A/B tests, p-values and Bayes' theorem](https://freecalculatorsonline.com/guides/ab-tests-p-values-bayes-guide): Learn what a p-value does and does not say, how to run a fair test, and why a positive result from a good test can still be wrong.
- [Comparing fuel economy: mpg, L/100 km and electric cars](https://freecalculatorsonline.com/guides/fuel-economy-mpg-ev-guide): Convert between fuel economy units, measure your real mileage and compare gasoline and electric cars on cost per mile.
- [How to read stock valuation ratios](https://freecalculatorsonline.com/guides/stock-valuation-ratios-guide): Understand P/E, PEG, dividend payout, earnings per share, market cap, enterprise value, book value and the Graham number, and what each one leaves out.
- [Sleep cycles and how to time a bedtime](https://freecalculatorsonline.com/guides/sleep-cycles-bedtime-guide): Understand what a sleep cycle is, how to count backward from a wake-up time and why the result is a scheduling aid and not a prescription.

## Tax & benefit calendar blog (8)

- [Tax Day Countdown: What Changes Before April 15](https://freecalculatorsonline.com/blog/tax-day-countdown-april-15): The federal filing deadline is usually April 15, but what actually needs to happen changes in stages well before that date: here's what each stage means.
- [How 401(k), IRA and HSA Limits Change Every January](https://freecalculatorsonline.com/blog/retirement-contribution-limits-new-year): 401(k), IRA and HSA limits are adjusted for inflation and announced each fall: check the current numbers, don't assume last year's still apply.
- [Why January Is the Best Time to Recheck Your Withholding](https://freecalculatorsonline.com/blog/w4-withholding-check-january): A withholding mismatch compounds every pay period it goes uncorrected. Checking it early in the year, not after many paychecks, limits how large it can grow.
- [The October 15 Tax Extension Deadline, Explained](https://freecalculatorsonline.com/blog/tax-extension-deadline-october): An extension filed in April buys until October to file paperwork, but the payment deadline never moved, and October 15 is a firmer, final date than April's.
- [The December 31 Deadline for Tax-Loss Harvesting](https://freecalculatorsonline.com/blog/year-end-tax-loss-harvesting-deadline): Realizing an investment loss to offset gains only counts for a given tax year if the trade settles by December 31. A deadline many investors discover too late.
- [FSA Year-End Deadlines: The Decision HSA Holders Skip](https://freecalculatorsonline.com/blog/fsa-year-end-use-it-or-lose-it): An HSA balance rolls over indefinitely; a standard FSA generally does not. The December decision is about the calendar, not which account is better.
- [Social Security's October COLA: What Changes, and When](https://freecalculatorsonline.com/blog/social-security-cola-announcement-october): Social Security's cost-of-living adjustment is announced in October but takes effect only in January. The gap trips up a lot of benefit planning.
- [The Four Estimated Tax Dates Self-Employed Filers Miss](https://freecalculatorsonline.com/blog/estimated-tax-payment-calendar): Estimated tax payments aren't due on a clean quarterly schedule. The four dates are unevenly spaced, and that spacing is what causes most missed payments.

## Glossary (174 terms)

Full glossary: https://freecalculatorsonline.com/glossary

- [Accrued interest](https://freecalculatorsonline.com/glossary/accrued-interest): Interest that has been earned on a security or loan but not yet paid. Bonds are quoted clean, without it, and settle dirty, with it added to the amount that changes hands.
- [Adjusted gross income](https://freecalculatorsonline.com/glossary/adjusted-gross-income): Total income less specific adjustments permitted before deductions are applied. Many credits and phase-outs are measured against it, not against taxable income.
- [After-tax return](https://freecalculatorsonline.com/glossary/after-tax-return): The return that remains once tax on income, distributions and gains is deducted. It is the only return an investor keeps, and it can rank two investments differently from their gross figures.
- [Amortization](https://freecalculatorsonline.com/glossary/amortization): The scheduled process of reducing a loan balance through payments that cover interest and principal.
- [Amortization schedule](https://freecalculatorsonline.com/glossary/amortization-schedule): The payment-by-payment table. It shows how each payment divides between interest and principal, and what balance remains after each one.
- [Annual percentage rate (APR)](https://freecalculatorsonline.com/glossary/annual-percentage-rate-apr): An annualized borrowing-cost measure that may include the interest rate and certain finance charges.
- [Annual percentage yield (APY)](https://freecalculatorsonline.com/glossary/annual-percentage-yield-apy): The effective annual deposit yield after the stated compounding frequency.
- [Annual recurring revenue (ARR)](https://freecalculatorsonline.com/glossary/annual-recurring-revenue-arr): A recurring-revenue run rate commonly calculated as monthly recurring revenue multiplied by twelve.
- [Annualized return](https://freecalculatorsonline.com/glossary/annualized-return): The compound yearly rate that links a beginning value to an ending value across a holding period.
- [Annuity](https://freecalculatorsonline.com/glossary/annuity): A series of equal payments made at regular intervals. An ordinary annuity pays at the end of each period. An annuity due pays at the start. That gives every payment one extra period of growth.
- [Asset allocation](https://freecalculatorsonline.com/glossary/asset-allocation): The distribution of a portfolio among asset classes or risk exposures.
- [Balloon payment](https://freecalculatorsonline.com/glossary/balloon-payment): A large final payment remaining after smaller scheduled loan payments.
- [Basal metabolic rate](https://freecalculatorsonline.com/glossary/basal-metabolic-rate): The energy the body uses at complete rest to maintain basic functions, before any activity is added.
- [Basis point](https://freecalculatorsonline.com/glossary/basis-point): One hundredth of one percentage point; 100 basis points equal 1 percentage point.
- [Bear market](https://freecalculatorsonline.com/glossary/bear-market): A sustained decline in a market, commonly defined as a fall of twenty percent or more from a recent peak. The twenty percent is a convention. Nothing technical marks that line.
- [Beta](https://freecalculatorsonline.com/glossary/beta): A measure of how much an asset has moved relative to a benchmark. A beta above one indicates larger swings than the benchmark historically, not a prediction that it will continue.
- [Billable utilization](https://freecalculatorsonline.com/glossary/billable-utilization): Billable hours divided by available working hours over the same period.
- [Blood alcohol concentration (BAC)](https://freecalculatorsonline.com/glossary/blood-alcohol-concentration-bac): The percentage of alcohol in the bloodstream, estimated by formula from drinks consumed, body weight, sex and elapsed time, or measured directly by breath or blood test.
- [Body mass index](https://freecalculatorsonline.com/glossary/body-mass-index): Weight relative to the square of height, used as a population-level screening measure. It does not distinguish muscle from fat.
- [Body surface area](https://freecalculatorsonline.com/glossary/body-surface-area): The total external surface area of the body, estimated from height and weight. Some clinical dosing and burn assessment work from it.
- [Bond coupon](https://freecalculatorsonline.com/glossary/bond-coupon): The cash interest payment a bond makes on each scheduled date. The coupon rate applied to face value sets its size. Rate is the percentage. Coupon is the money that changes hands.
- [Bond duration](https://freecalculatorsonline.com/glossary/bond-duration): A present-value-weighted timing measure used to approximate bond-price sensitivity to yield changes.
- [Book value](https://freecalculatorsonline.com/glossary/book-value): The value of an asset in the accounts, generally cost less accumulated depreciation. It frequently differs from market value, and the gap matters when an asset is sold.
- [Break-even point](https://freecalculatorsonline.com/glossary/break-even-point): The volume at which total revenue equals total costs. It moves whenever the cost structure changes. Treat it as a range, not a point: fixed costs are only fixed within a capacity band.
- [Burn rate](https://freecalculatorsonline.com/glossary/burn-rate): The rate at which an organization consumes cash, often measured monthly.
- [Capital expenditure](https://freecalculatorsonline.com/glossary/capital-expenditure): Spending on assets with a useful life beyond the current period, capitalised and depreciated, not expensed immediately. In property, the reserve for roofs, systems and appliances.
- [Capital gains](https://freecalculatorsonline.com/glossary/capital-gains): The difference between disposition proceeds and adjusted basis after applicable selling costs.
- [Capitalization rate](https://freecalculatorsonline.com/glossary/capitalization-rate): A property’s annual net operating income divided by its price or value.
- [Cash conversion cycle](https://freecalculatorsonline.com/glossary/cash-conversion-cycle): Inventory days plus receivable days minus payable days.
- [Cash-on-cash return](https://freecalculatorsonline.com/glossary/cash-on-cash-return): Annual pre-tax property cash flow divided by the cash invested.
- [CIDR notation](https://freecalculatorsonline.com/glossary/cidr-notation): The slash-prefix shorthand (e.g. /24) that states how many leading bits of an IP address are the fixed network portion. A smaller number after the slash means a larger network with more usable addresses.
- [Collateral](https://freecalculatorsonline.com/glossary/collateral): An asset pledged to secure a loan, which the lender can claim on default. Its presence lowers lender risk and usually the rate, at the cost of the asset being at stake.
- [Combination](https://freecalculatorsonline.com/glossary/combination): A selection of items where order does not matter. Choosing 3 people for a committee from a group is a combination problem.
- [Compound annual growth rate (CAGR)](https://freecalculatorsonline.com/glossary/compound-annual-growth-rate-cagr): The constant annual rate that would link a beginning value to an ending value over a period.
- [Compound interest](https://freecalculatorsonline.com/glossary/compound-interest): Growth calculated on principal and accumulated prior growth.
- [Compounding frequency](https://freecalculatorsonline.com/glossary/compounding-frequency): How often accrued interest is added to the balance so it begins earning in turn. More frequent compounding raises the effective rate, with a hard ceiling at continuous compounding.
- [Confidence interval](https://freecalculatorsonline.com/glossary/confidence-interval): A range built from sample data. It is likely to contain the true population value at a stated confidence level, commonly 95%.
- [Contribution margin](https://freecalculatorsonline.com/glossary/contribution-margin): Revenue remaining after variable costs, available to cover fixed costs and profit.
- [Convexity](https://freecalculatorsonline.com/glossary/convexity): The curvature of the relationship between a bond's price and its yield. It corrects duration, which is a straight-line approximation and grows less accurate as the yield move gets larger.
- [Cost basis](https://freecalculatorsonline.com/glossary/cost-basis): The amount used to measure gain or loss on disposal, generally purchase price plus certain adjustments. An incorrect basis produces an incorrect gain and an incorrect tax figure.
- [Coupon rate](https://freecalculatorsonline.com/glossary/coupon-rate): The annual interest a bond pays as a percentage of its face value. It is fixed at issue, which is why the price must move when market yields change.
- [Credit hour](https://freecalculatorsonline.com/glossary/credit-hour): A unit measuring the classroom time or coursework value of a course. Each grade is weighted by it in a GPA calculation.
- [Credit utilization](https://freecalculatorsonline.com/glossary/credit-utilization): Reported revolving credit balances divided by total reported revolving credit limits.
- [Current ratio](https://freecalculatorsonline.com/glossary/current-ratio): Current assets divided by current liabilities.
- [Current yield](https://freecalculatorsonline.com/glossary/current-yield): A bond’s annual coupon cash flow divided by its current market price.
- [Debt-service coverage ratio (DSCR)](https://freecalculatorsonline.com/glossary/debt-service-coverage-ratio-dscr): Income available for debt service divided by required debt service.
- [Debt-to-income ratio (DTI)](https://freecalculatorsonline.com/glossary/debt-to-income-ratio-dti): Required monthly debt payments divided by gross monthly income.
- [Deductible](https://freecalculatorsonline.com/glossary/deductible): The amount paid toward covered costs before an insurer begins paying. It sits ahead of coinsurance in the payment sequence and below the out-of-pocket maximum.
- [Depreciation](https://freecalculatorsonline.com/glossary/depreciation): The allocation of an asset's cost across its useful life. An accounting and tax concept distinct from the asset's actual change in market value.
- [Determinant](https://freecalculatorsonline.com/glossary/determinant): A single number computed from a square matrix that determines whether it can be inverted. A zero determinant means the matrix has no inverse.
- [Dew point](https://freecalculatorsonline.com/glossary/dew-point): The temperature air would need to cool to for it to become fully saturated with the moisture it currently holds. A higher dew point means more humid, muggier air.
- [Discount rate](https://freecalculatorsonline.com/glossary/discount-rate): The rate used to convert future cash flows into present value.
- [Discriminant](https://freecalculatorsonline.com/glossary/discriminant): The b²−4ac term inside the quadratic formula, calculated before taking the square root. Its sign alone tells you what kind of solution to expect. Positive means two distinct real roots. Zero means one repeated real root. Negative means no real roots at all, only a complex pair, and those fall outside what a real-number calculator can display.
- [Diversification](https://freecalculatorsonline.com/glossary/diversification): Holding assets whose returns do not move together, reducing exposure to any single holding. It reduces specific risk and does not remove market-wide risk.
- [Dividend yield](https://freecalculatorsonline.com/glossary/dividend-yield): Annual dividends as a percentage of share price. It rises when the price falls. So a high yield can signal a falling price. It is not always a generous distribution.
- [Dollar-cost averaging](https://freecalculatorsonline.com/glossary/dollar-cost-averaging): Investing a fixed amount on a recurring schedule regardless of market price.
- [Drawdown](https://freecalculatorsonline.com/glossary/drawdown): The percentage decline from a prior peak to a subsequent trough.
- [Duration](https://freecalculatorsonline.com/glossary/duration): The umbrella term for how long a bond's money effectively takes to arrive. That timing decides how much its price moves when yields change. Two specific forms exist and they are not interchangeable. Macaulay duration is a present-value-weighted time in years. Modified duration is a percentage price sensitivity. Longer maturity and lower coupon increase both.
- [DV01](https://freecalculatorsonline.com/glossary/dv01): The approximate dollar price change of a bond or portfolio for a one-basis-point yield change.
- [Effective annual rate](https://freecalculatorsonline.com/glossary/effective-annual-rate): The annual rate accounting for compounding within the year. The figure that makes two differently-compounded quotes genuinely comparable.
- [Effective tax rate](https://freecalculatorsonline.com/glossary/effective-tax-rate): Estimated total tax divided by the selected income measure.
- [Emergency fund](https://freecalculatorsonline.com/glossary/emergency-fund): Liquid money reserved for income disruption or genuinely unexpected essential expenses.
- [Enterprise value](https://freecalculatorsonline.com/glossary/enterprise-value): A business value measure representing operating assets before allocating value between debt and equity.
- [Epoch day](https://freecalculatorsonline.com/glossary/epoch-day): A whole-number count of days since January 1, 1970. Date calculators use it internally, so date arithmetic reduces to integer subtraction.
- [Equity](https://freecalculatorsonline.com/glossary/equity): The owner's share of an asset's value after debts against it. In property, value less the outstanding balance; in a company, assets less liabilities.
- [Escrow](https://freecalculatorsonline.com/glossary/escrow): An account holding funds for property tax and insurance, paid out when due. It changes the timing of those costs, never the total.
- [Exchange rate](https://freecalculatorsonline.com/glossary/exchange-rate): The price of one currency stated in units of another. Published reference rates like the ECB's are the neutral benchmark. A bank, card network or exchange adds its own spread on top of that.
- [Expense ratio](https://freecalculatorsonline.com/glossary/expense-ratio): An investment fund’s annual operating expenses expressed as a percentage of assets.
- [Face value](https://freecalculatorsonline.com/glossary/face-value): The amount a bond repays at maturity, also called par. Coupons are calculated on it, and market price can sit above or below it.
- [Factorial](https://freecalculatorsonline.com/glossary/factorial): The product of a whole number and every positive whole number below it, written n!. Used to count arrangements and combinations; 0! is defined as 1.
- [Fiduciary](https://freecalculatorsonline.com/glossary/fiduciary): A party legally obliged to act in another's best interest. The standard is higher than suitability, which requires only that a recommendation be appropriate.
- [Financial independence (FIRE)](https://freecalculatorsonline.com/glossary/financial-independence-fire): A condition in which assets and other dependable income are modeled to support ongoing spending without employment income.
- [Fixed cost](https://freecalculatorsonline.com/glossary/fixed-cost): A cost that does not vary with output within a given capacity range. Cross that range and it steps up.
- [Free cash flow](https://freecalculatorsonline.com/glossary/free-cash-flow): Cash from operations less capital expenditure: what the business generates after maintaining its asset base. Distinct from profit, which is an accrual measure.
- [Future value](https://freecalculatorsonline.com/glossary/future-value): The modeled value of money at a future date after growth and cash flows.
- [Gestational weight gain](https://freecalculatorsonline.com/glossary/gestational-weight-gain): Weight gained during pregnancy, The recommended range is set by pre-pregnancy BMI category. There is no single target for everyone.
- [Glomerular filtration rate (GFR)](https://freecalculatorsonline.com/glossary/glomerular-filtration-rate-gfr): A measure of how well the kidneys filter blood. It is usually estimated from a blood creatinine level, age and sex. Direct measurement is rare.
- [Grade point average (GPA)](https://freecalculatorsonline.com/glossary/grade-point-average-gpa): Total quality points earned divided by total credit hours attempted, most commonly on a 4.0 scale. No single national standard exists: schools set their own scale and rounding.
- [Greatest common factor (GCF)](https://freecalculatorsonline.com/glossary/greatest-common-factor-gcf): The largest number that divides two or more numbers evenly. It reduces fractions and ratios to their smallest whole-number form.
- [Gross margin](https://freecalculatorsonline.com/glossary/gross-margin): Revenue minus cost of goods sold, divided by revenue.
- [Gross rent multiplier (GRM)](https://freecalculatorsonline.com/glossary/gross-rent-multiplier-grm): Property price divided by annual gross rent before expenses.
- [Gross revenue retention (GRR)](https://freecalculatorsonline.com/glossary/gross-revenue-retention-grr): Recurring revenue retained from a starting cohort after churn and contraction, excluding expansion.
- [Heart-rate reserve](https://freecalculatorsonline.com/glossary/heart-rate-reserve): The difference between maximum and resting heart rate. The Karvonen method uses it to scale a target training intensity to an individual's own range.
- [Heat index](https://freecalculatorsonline.com/glossary/heat-index): A calculated "feels-like" temperature that combines air temperature and relative humidity to estimate how hot the body actually perceives conditions to be.
- [Heron's formula](https://freecalculatorsonline.com/glossary/heron-s-formula): A method for calculating a triangle's area from its three side lengths alone, without needing a separate height measurement. The method computes the semi-perimeter, half the sum of the three sides, then combines it with each side under a square root. Unlike the base-times-height formula, it applies to any triangle. Right, obtuse or scalene. The only condition is that the three lengths can actually form one.
- [Home equity](https://freecalculatorsonline.com/glossary/home-equity): Property value less debts secured by the property.
- [Home equity line of credit](https://freecalculatorsonline.com/glossary/home-equity-line-of-credit): A revolving credit line secured by property, usually at a variable rate. A draw period comes first, then a repayment period. The payment usually rises sharply at the handover.
- [Index fund](https://freecalculatorsonline.com/glossary/index-fund): A fund that tracks a published index instead of selecting holdings. Its case rests on low cost and broad exposure, not on selection skill.
- [Inflation](https://freecalculatorsonline.com/glossary/inflation): The rate at which prices rise and purchasing power falls. It compounds, which is why long-horizon plans built on nominal figures overstate what will be affordable.
- [Interest-only period](https://freecalculatorsonline.com/glossary/interest-only-period): A phase during which payments cover only accruing interest and the balance does not fall. The later payment rises twice over: amortization begins, and over fewer remaining years.
- [Internal rate of return (IRR)](https://freecalculatorsonline.com/glossary/internal-rate-of-return-irr): A discount rate that sets the net present value of modeled cash flows to zero.
- [Lean body mass](https://freecalculatorsonline.com/glossary/lean-body-mass): Total body weight minus estimated fat mass, covering muscle, bone, organs and water.
- [Least common multiple (LCM)](https://freecalculatorsonline.com/glossary/least-common-multiple-lcm): The smallest number that two or more numbers all divide into evenly. Used for common denominators and for aligning repeating cycles.
- [Liquidity](https://freecalculatorsonline.com/glossary/liquidity): How quickly an asset converts to cash without a material loss of value. An asset can be valuable and illiquid, which is what makes reserves necessary.
- [Loan-to-value ratio (LTV)](https://freecalculatorsonline.com/glossary/loan-to-value-ratio-ltv): Loan balance divided by property value.
- [Macronutrient](https://freecalculatorsonline.com/glossary/macronutrient): One of the three nutrients supplying dietary energy, protein, carbohydrate and fat, each with a different calories-per-gram value.
- [Margin of error](https://freecalculatorsonline.com/glossary/margin-of-error): The plus-or-minus range added to a sample estimate to build a confidence interval. Sample size, variability and the chosen confidence level drive it.
- [Marginal tax rate](https://freecalculatorsonline.com/glossary/marginal-tax-rate): The tax rate applied to the next dollar within a simplified bracket analysis.
- [Markup](https://freecalculatorsonline.com/glossary/markup): Selling price minus cost, divided by cost.
- [Maximum drawdown](https://freecalculatorsonline.com/glossary/maximum-drawdown): The largest peak-to-trough decline over a period. It describes the worst moment an investor had to sit through, which predicts abandonment better than volatility does.
- [Metabolic equivalent (MET)](https://freecalculatorsonline.com/glossary/metabolic-equivalent-met): A unit expressing the energy cost of an activity as a multiple of resting metabolic rate. A MET of 1 approximates sitting quietly.
- [Modified duration](https://freecalculatorsonline.com/glossary/modified-duration): Macaulay duration divided by one plus yield per payment period; a first-order estimate of price sensitivity.
- [Molarity](https://freecalculatorsonline.com/glossary/molarity): The concentration of a solution expressed as moles of dissolved solute per liter of solution.
- [Money factor](https://freecalculatorsonline.com/glossary/money-factor): How a lease expresses its finance charge. Multiply by 2,400 for an approximate equivalent annual interest rate.
- [Money-weighted return](https://freecalculatorsonline.com/glossary/money-weighted-return): A return measure affected by the timing and amount of investor-controlled cash flows.
- [Monthly recurring revenue (MRR)](https://freecalculatorsonline.com/glossary/monthly-recurring-revenue-mrr): Recurring subscription value normalized to one month under a stated revenue policy.
- [Naegele's rule](https://freecalculatorsonline.com/glossary/naegele-s-rule): The standard obstetric convention for estimating a due date: 280 days, or 40 weeks, after the first day of the last menstrual period. It assumes a textbook 28-day cycle and is superseded by ultrasound dating when the two disagree.
- [Net operating income (NOI)](https://freecalculatorsonline.com/glossary/net-operating-income-noi): Property operating income after operating expenses and before financing, depreciation and investor income tax.
- [Net present value](https://freecalculatorsonline.com/glossary/net-present-value): The sum of future cash flows discounted to today, less the initial outlay. A positive figure indicates the flows exceed the required return at the chosen discount rate.
- [Net revenue retention](https://freecalculatorsonline.com/glossary/net-revenue-retention): Revenue from an existing customer cohort at period end against its start. Expansion, contraction and churn count. New customers do not.
- [Nominal rate](https://freecalculatorsonline.com/glossary/nominal-rate): A quoted rate before adjusting for compounding frequency or inflation. Comparing a nominal rate to a real one is a common source of a plan that appears funded and is not.
- [Ohm's law](https://freecalculatorsonline.com/glossary/ohm-s-law): The relationship V = I × R linking voltage, current and resistance in a purely resistive electrical circuit.
- [One-rep max](https://freecalculatorsonline.com/glossary/one-rep-max): The heaviest weight a person can lift for one complete repetition. Usually estimated from a lighter set taken near failure.
- [Opportunity cost](https://freecalculatorsonline.com/glossary/opportunity-cost): The value of the best alternative forgone. It is why a deposit that builds equity is not free: the same cash could have been invested elsewhere.
- [Origination fee](https://freecalculatorsonline.com/glossary/origination-fee): A charge for processing a loan, deducted from proceeds or added to the balance. It changes effective cost without changing the payment, which is what APR captures.
- [Out-of-pocket maximum](https://freecalculatorsonline.com/glossary/out-of-pocket-maximum): The most a plan requires you to pay toward covered in-network care in a year. The figure that defines the worst case when comparing health plans.
- [Password entropy](https://freecalculatorsonline.com/glossary/password-entropy): A measure, in bits, of how unpredictable a password is: the base-2 logarithm of how many equally likely passwords share the same length and character pool. Higher entropy means an exhaustive guessing attack takes longer on average.
- [Payback period](https://freecalculatorsonline.com/glossary/payback-period): The time for cumulative cash inflows to recover an initial outlay. Simple and blind to everything that happens after recovery.
- [Percent error](https://freecalculatorsonline.com/glossary/percent-error): How far a measured value sits from the known or theoretical one. Expressed as a percentage of the theoretical value.
- [Permutation](https://freecalculatorsonline.com/glossary/permutation): An arrangement of items where order matters. Picking a first, second and third place from a group is a permutation problem.
- [Points](https://freecalculatorsonline.com/glossary/points): An upfront charge, each typically one percent of the loan, paid to lower the rate. Worthwhile only if the loan is held past the break-even.
- [Pre-pregnancy BMI](https://freecalculatorsonline.com/glossary/pre-pregnancy-bmi): Body mass index calculated from weight before conception, used as the standard starting point for recommended pregnancy weight-gain ranges.
- [Prepayment penalty](https://freecalculatorsonline.com/glossary/prepayment-penalty): A charge for repaying a loan early, which reduces or eliminates the saving from paying ahead. Its presence should be checked before assuming early payoff saves the remaining interest.
- [Present value](https://freecalculatorsonline.com/glossary/present-value): The current amount equivalent to a future cash flow under a selected discount rate.
- [Prime factorization](https://freecalculatorsonline.com/glossary/prime-factorization): Breaking a number down into the prime numbers that multiply together to produce it. Every whole number greater than 1 has exactly one such breakdown.
- [Principal](https://freecalculatorsonline.com/glossary/principal): The amount borrowed or invested, before interest. Interest on an amortizing loan is charged on the outstanding principal, which is why early payments are mostly interest.
- [Private mortgage insurance (PMI)](https://freecalculatorsonline.com/glossary/private-mortgage-insurance-pmi): Insurance that may be required on certain conventional mortgages with higher loan-to-value ratios.
- [Progressive tax](https://freecalculatorsonline.com/glossary/progressive-tax): A system where higher slices of income are taxed at higher rates. Crossing a bracket reprices only the income above the threshold, never what came before.
- [Quality points](https://freecalculatorsonline.com/glossary/quality-points): A course's grade points multiplied by its credit hours; quality points summed across courses, divided by total credit hours, produce GPA.
- [Quick ratio](https://freecalculatorsonline.com/glossary/quick-ratio): Quick assets divided by current liabilities, generally excluding inventory.
- [Radian](https://freecalculatorsonline.com/glossary/radian): A unit of angle based on the radius of a circle: one full turn equals 2π radians. Trigonometric functions in most programming languages expect radians, not degrees.
- [Real rate of return](https://freecalculatorsonline.com/glossary/real-rate-of-return): The return after inflation: the only measure describing a change in purchasing power. A healthy nominal return during similar inflation is no real gain at all.
- [Rebalancing](https://freecalculatorsonline.com/glossary/rebalancing): Restoring a portfolio to its target allocation by selling what has risen and buying what has fallen. The discipline, not the timing, is the benefit.
- [Recast](https://freecalculatorsonline.com/glossary/recast): Recalculating a loan payment after a lump-sum principal reduction, keeping the original term. It lowers the payment where prepaying alone would shorten the term instead.
- [Refinance](https://freecalculatorsonline.com/glossary/refinance): Replacing an existing loan with a new one, resetting the term and incurring closing costs. The only one of prepay, recast and refinance that can change the rate.
- [Required minimum distribution (RMD)](https://freecalculatorsonline.com/glossary/required-minimum-distribution-rmd): A minimum retirement-account distribution calculated under current rules using an applicable balance and life-expectancy factor.
- [Return on ad spend (ROAS)](https://freecalculatorsonline.com/glossary/return-on-ad-spend-roas): Revenue attributed to advertising divided by advertising spend.
- [Return on investment (ROI)](https://freecalculatorsonline.com/glossary/return-on-investment-roi): Net gain divided by the investment cost used as the denominator.
- [Risk-free rate](https://freecalculatorsonline.com/glossary/risk-free-rate): The return on an asset assumed to carry no default risk, used as the baseline in risk-adjusted measures. Changing which rate is used changes every such measure.
- [Roofing square](https://freecalculatorsonline.com/glossary/roofing-square): A roofing-industry unit equal to 100 square feet of roof surface. Shingles and underlayment are priced and packaged by it. A typical bundle of asphalt shingles covers roughly a third of a square. So estimates are given in squares first. Conversion to bundles or rolls comes afterward, once the specific product's coverage rate is known.
- [Runway](https://freecalculatorsonline.com/glossary/runway): The estimated time available before unrestricted cash is depleted at a modeled net burn rate.
- [Safe harbor](https://freecalculatorsonline.com/glossary/safe-harbor): A payment threshold that can reduce estimated-tax underpayment exposure when current rules are met.
- [Seller’s discretionary earnings (SDE)](https://freecalculatorsonline.com/glossary/seller-s-discretionary-earnings-sde): A small-business earnings measure that may add back one owner’s compensation and selected discretionary or nonrecurring items.
- [Serum creatinine](https://freecalculatorsonline.com/glossary/serum-creatinine): A waste product from muscle metabolism, measured in blood. Most eGFR equations use it as their primary input, because the kidneys are the main route it leaves the body.
- [Sharpe ratio](https://freecalculatorsonline.com/glossary/sharpe-ratio): Excess return divided by total return volatility for the same measurement period.
- [Simple interest](https://freecalculatorsonline.com/glossary/simple-interest): Interest charged only on the original principal, never on accumulated interest. Distinct from amortizing interest, which is charged on the declining balance.
- [Sinking fund](https://freecalculatorsonline.com/glossary/sinking-fund): Money accumulated gradually for a known future expense.
- [Solo 401(k)](https://freecalculatorsonline.com/glossary/solo-401-k): A 401(k) for a self-employed person or owner-only business. One person contributes as both employee and employer. That dual capacity is why it can exceed a SEP IRA at the same income.
- [Sortino ratio](https://freecalculatorsonline.com/glossary/sortino-ratio): Excess return divided by downside deviation relative to a target.
- [Specific gravity](https://freecalculatorsonline.com/glossary/specific-gravity): A substance's density relative to water. Values above 1 sink in water; values below 1 float.
- [Standard deduction](https://freecalculatorsonline.com/glossary/standard-deduction): A fixed amount subtracted from income instead of itemising. Because it is substantial, many households receive no incremental benefit from deductible expenses.
- [Standard deviation](https://freecalculatorsonline.com/glossary/standard-deviation): A measure of how spread out a set of values is around its mean. A small standard deviation means values cluster tightly; a large one means they scatter widely.
- [Standard drink](https://freecalculatorsonline.com/glossary/standard-drink): A reference serving containing a fixed amount of pure alcohol (14 grams in the United States), used to compare drinks of different type and size on a common basis.
- [Subnet mask](https://freecalculatorsonline.com/glossary/subnet-mask): A 32-bit value that marks which bits of an IP address are the network portion versus the host portion. A wildcard mask is its exact bitwise inverse.
- [Tax-deferred](https://freecalculatorsonline.com/glossary/tax-deferred): An arrangement where tax is postponed until withdrawal instead of being paid as growth occurs. The full amount compounds in the meantime.
- [Tax-equivalent yield](https://freecalculatorsonline.com/glossary/tax-equivalent-yield): The taxable yield needed to equal a tax-exempt yield at an assumed marginal tax rate.
- [Term](https://freecalculatorsonline.com/glossary/term): The length of a loan or the period of an insurance policy. On a loan it is the strongest lever on total cost and the weakest on the payment.
- [Time value of money](https://freecalculatorsonline.com/glossary/time-value-of-money): The principle that money available now is worth more than the same amount later, because it can earn a return. The foundation under discounting and present value.
- [Time-weighted return](https://freecalculatorsonline.com/glossary/time-weighted-return): A linked return measure designed to reduce the effect of external cash-flow timing.
- [Total cost of ownership](https://freecalculatorsonline.com/glossary/total-cost-of-ownership): Every cost of owning an asset over its life, purchase, financing, insurance, fuel, maintenance, repairs and disposal, not just the payment.
- [Total daily energy expenditure](https://freecalculatorsonline.com/glossary/total-daily-energy-expenditure): Basal metabolic rate multiplied by an activity factor: an estimate of total calories burned in a day including movement and exercise.
- [Training pace](https://freecalculatorsonline.com/glossary/training-pace): Speed expressed as time per unit distance, not distance per unit time. Minutes per mile is the common U.S. running convention.
- [Turnover](https://freecalculatorsonline.com/glossary/turnover): How much of a portfolio is traded in a year. High turnover implies higher internal trading costs and, in a taxable account, more distributions and more current tax.
- [Underwater](https://freecalculatorsonline.com/glossary/underwater): Owing more on an asset than it is worth. Common early in a long vehicle loan because depreciation is front-loaded while principal reduction is not.
- [Variable cost](https://freecalculatorsonline.com/glossary/variable-cost): A cost that changes with output. Subtracted from price to give contribution margin, the figure that drives break-even.
- [Vesting](https://freecalculatorsonline.com/glossary/vesting): The process by which a right to an asset or contribution becomes non-forfeitable over time. Unvested employer contributions are lost if employment ends first.
- [Volatility](https://freecalculatorsonline.com/glossary/volatility): The dispersion of returns around their average, usually standard deviation. It treats gains and losses identically, which is why it is a poor standalone definition of risk.
- [Waist-to-hip ratio](https://freecalculatorsonline.com/glossary/waist-to-hip-ratio): Waist circumference divided by hip circumference, used alongside BMI to describe where body fat is carried.
- [Weighted average cost of capital](https://freecalculatorsonline.com/glossary/weighted-average-cost-of-capital): The blended cost of a company's debt and equity financing, weighted by their proportions. The usual discount rate for evaluating a company's own investments.
- [Weighted GPA](https://freecalculatorsonline.com/glossary/weighted-gpa): A GPA variant that adds bonus grade points before averaging, so harder courses can outscore easier ones. Honors commonly earns +0.5 and AP, IB or college-level work +1.0. The bonus and cap vary by school.
- [Working capital](https://freecalculatorsonline.com/glossary/working-capital): Current assets minus current liabilities.
- [Yield to maturity (YTM)](https://freecalculatorsonline.com/glossary/yield-to-maturity-ytm): The discount rate that equates a bond’s scheduled cash flows to its market price under stated assumptions.
- [Z-score](https://freecalculatorsonline.com/glossary/z-score): How many standard deviations a value sits from the mean of its distribution. A z-score of 2 means the value is two standard deviations above average.
- [Zero-coupon bond](https://freecalculatorsonline.com/glossary/zero-coupon-bond): A bond paying no periodic interest, bought below face value and maturing at face. Its entire return is the difference, which makes it unusually sensitive to rate changes.

## Reference pages

- [All calculators](https://freecalculatorsonline.com/calculators): searchable index of all 654
- [Current rate centre](https://freecalculatorsonline.com/rates): dated Freddie Mac survey averages and U.S. Treasury par yields
- [Questions answered](https://freecalculatorsonline.com/answers): direct answers with the formula and a working calculator
- [Frequently asked questions](https://freecalculatorsonline.com/faq): how the site works, privacy, accuracy and corrections
- [Comparison calculators](https://freecalculatorsonline.com/comparisons): side-by-side decision tools
- [Methodology](https://freecalculatorsonline.com/resources/methodology): how formulas are defined, tested and reviewed
- [Editorial policy](https://freecalculatorsonline.com/resources/editorial-policy)
- [Source ledger](https://freecalculatorsonline.com/resources/sources)
- [Corrections](https://freecalculatorsonline.com/resources/corrections)
- [AI citation policy](https://freecalculatorsonline.com/resources/ai-citation-policy)