Library scope
663 calculators across 42 categories, 46 guides and 174 defined terms, supported by 63 primary sources. Every calculator declares a formula, at least one input, at least two outputs, an interpretation, a limitation boundary and at least one source; a calculator missing any of these fails the automated suite and is not released.
Evidence on the page
Each calculator page publishes a worked example computed from its prefilled inputs, a sensitivity table recomputing the headline result across a range of the input that drives it, and, on 596 of the 663 pages, wherever two inputs are both meaningful, a two-variable grid. Where the formula produces a schedule, every row of it is published, not a sample.
Link integrity
A repository command requests every internal link and every URL named inside structured data against the running site and reports how many did not return 200. It is run before release and the count has to be zero.
What this record does not claim
These checks establish that the arithmetic matches the published formula and that the pages are internally consistent. They cannot establish that a formula is the right model for your situation, that a rule has not changed since the review date, or that a figure you entered is accurate. Those remain your judgement, and the interpretation boundary on each page states the limits we know about.
Formula verification
Core formulas are checked against a second implementation that arrives at the answer by a different route: closed-form loan payments against a month-by-month simulation, bond price against explicitly discounted cash flows, compound growth against period-by-period accumulation, and income tax against an independent bracket walk. Agreement between two different methods is materially stronger evidence than one method being run twice.
Boundary and stress testing
Each one is run at its worked-example inputs, at zero, and at extreme values in both directions. The suite fails if any result returns infinity, if a result that should be defined becomes undefined, or if any calculator takes long enough to stall a browser. These checks exist because arithmetic that is correct in the normal range can still fail at the edges, and users reach the edges.
What a review date means here
A review date states when the calculation and its supporting text were last checked against their sources. A review date does not certify that no external rule has changed since. Nor is it a guarantee of suitability for any particular decision. Where a figure depends on a statutory value that changes annually, the page says so and names the authority to check , not implying permanence.
How to challenge a figure
Any published figure can be disputed by naming the page, the inputs used, the result obtained, the result expected, and the basis for expecting it. Enough information to reproduce the calculation and either confirm the error or explain the difference. Corrections that change a result are applied to the page, the review date, and any dependent calculator.
The record in numbers
| What | Count |
|---|---|
| Calculators | 663 |
| Categories | 42 |
| Guides | 46 |
| Defined terms | 174 |
| Primary sources | 63 |
| Calculators with a two-variable grid | 596 |
| Calculators that publish a full schedule | 35 |
| Calculators with a per-input analysis | 632 |
Frequently asked questions
What is checked before a calculator is published?
Every calculator declares a formula, at least one input, at least two outputs, an interpretation, a limitation boundary and at least one source. A calculator missing any of these fails the automated suite and is not released.
How large is the library this record covers?
663 calculators across 42 categories, 46 guides and 174 defined terms, supported by 63 primary sources.
How are core formulas verified independently?
Against a second implementation that arrives at the answer by a different route: closed-form loan payments against a month-by-month simulation, bond price against explicitly discounted cash flows, compound growth against period-by-period accumulation, and income tax against an independent bracket walk.
What happens at zero and at extreme values?
Each calculator is run at its worked-example inputs, at zero and at extreme values in both directions. The suite fails if any result returns infinity, if a result that should be defined becomes undefined, or if any calculator takes long enough to stall a browser.
Are links checked?
Yes. A repository command requests every internal link and every URL named inside structured data against the running site. The command is run before release, and the count of links that did not return 200 has to be zero.
How many pages have a two-variable grid?
596 of 663 calculator pages, wherever two inputs are both meaningful.
Is a full schedule published or only a sample?
The full schedule, every row. 35 calculators produce one, and each also exports it as CSV.
What does this record not claim?
The record establishes that the arithmetic matches the published formula and that pages are internally consistent, but it cannot establish that a formula is the right model for your situation, that a rule has not changed since the review date, or that a figure you entered is accurate.