Compounding frequency

Before you rely on it

What to check

Convert both quotes to an effective annual figure before ranking them.

The common error

Where people go wrong with compounding frequency

Comparing a monthly-compounded loan rate to a daily-compounded savings rate as if they were the same unit. They are not, and the comparison quietly favours whichever one was quoted more generously.

Worked through

Compounding frequency in plain numbers

Take a stated rate of 6% a year. Compounded annually, $1,000 becomes $1,060 after one year, an effective yield of 6.000%. Compounded monthly, each month earns 0.5%, and the year ends at $1,061.68, or 6.168%. Compounded daily, the result is $1,061.83, or 6.183%. Even compounding continuously, the limit, only reaches $1,061.84. So the jump from annual to monthly adds 0.168 points, while going from daily to continuous adds about a cent on $1,000; most of the benefit arrives early. Beyond monthly, the gains are tiny.

Easily confused

Compounding frequency and its neighbours

Compounding frequency is not the same as the payment frequency, though both can be monthly; a savings account may compound daily and credit interest monthly. It is also distinct from the stated rate: two accounts with the same stated rate and different frequencies have different effective yields; the APY and effective annual rate fold the frequency into one figure so you can compare. The stated, or nominal, rate alone can mislead. Always ask both how often interest compounds and what the effective annual figure is.

In real decisions

Where compounding frequency turns up

You see frequency on savings accounts, CDs, bonds, loans and credit cards. On a loan, more frequent compounding raises the cost slightly. On a deposit, it raises what you earn. Mortgage terms in some countries specify semiannual compounding, which affects the payment; comparing accounts is easiest when both are converted to APY. Financial models set the frequency to match the product, and a mismatch can throw a projection off by a noticeable amount over long periods.

Know the edges

Where compounding frequency stops being reliable

Beyond a certain point more frequent compounding barely matters, so a difference between daily and monthly is not usually worth chasing. Bigger differences come from the rate itself, from fees and from balance requirements; some accounts credit interest only if the money stays for a minimum period. When comparing offers, look at the effective yield, the fine print on when interest posts and any conditions; a slightly lower rate with fewer strings can be the better deal.

Quick answers

What people ask about compounding frequency

Does daily compounding beat monthly by much? Rarely. At 5% the difference in the year-end balance is about a dollar on $10,000. The rate, fees and balance requirements matter more.

Where do I find how often my account compounds? In the account terms or disclosure. Look for compounding and crediting schedule. Some accounts compound daily but credit interest monthly. Ask the bank if the disclosure is unclear.

Is continuous compounding real? It is a mathematical limit used in models. Real accounts compound at set intervals. The continuous result, e raised to the rate, is the upper bound for a given nominal rate.

What is the difference between compounding and crediting? Compounding is how often interest is calculated on the growing balance. Crediting is when it is posted to your account. Some accounts compound daily but credit monthly.