The formulas
- EAR = (1 + APR / m)^m - 1
- Continuous: EAR = e^APR - 1
- Periodic rate = APR / m
How it works
The APR quoted on a loan or card is a nominal rate: the periodic rate times the number of periods. When interest compounds, each period charges interest on earlier interest, so the effective annual rate is higher. The gap widens with the rate and the compounding frequency.
Credit cards that compound daily charge APR / 365 each day on the balance. A 24.99 percent APR becomes 28.38 percent a year on a balance left unpaid all year. Use EAR to compare offers with different compounding.
Illustrative figures only. Check the result against your firm's methodology before relying on it.
Common questions
Is APY the same as EAR?
Yes. Deposit accounts quote APY, which is the effective annual rate.
Why does my card statement show a daily rate?
Card issuers apply APR / 365 or APR / 360 to the daily balance. Check your agreement.
Does continuous compounding matter in practice?
It is the upper limit. Daily compounding is within a few basis points of it.
Formulas on this page are the standard definitions.
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