Honest InterestAPR, APY & credit card payoff calculators

Calculator 01 · Rates

APR to APY converter

The APR is the rate on the label. The APY is what a year of compounding does with it. Enter either one, pick how often interest is added, and see both side by side at every frequency.

Your figuresp. 1

I know the

The card example fills in a 22% APR charged daily, to show what compounding does to a balance you carry.

The answerp. 2

APY · Monthly5.116%

A year's interest on $10,000.00$511.62

An APR of 5.00% compounded monthly grows by 5.116% over a year. The APY is 0.116% points higher because interest earns interest.

5.00% APR at every compounding frequency, on $10,000.00
LineCompoundingTimes a yearRate per periodAPYA year's interest
01Annually15.0000%5.000%$500.00
02Semi-annually22.5000%5.063%$506.25
03Quarterly41.2500%5.095%$509.45
04Monthly (chosen)120.4167%5.116%$511.62
05Twice a month240.2083%5.122%$512.16
06Every two weeks260.1923%5.122%$512.21
07Weekly520.0962%5.125%$512.46
08Daily (365)3650.0137%5.127%$512.67
09Continuously∞—5.127%$512.71

Educational use only — not financial advice. The rate is whatever you type in; nothing here is an offer, a quote or a forecast.

What the two numbers mean

An APR (annual percentage rate) is a yearly rate before compounding. Divide it by the number of compounding periods and you get the rate added each period: 5% APR compounded monthly is 0.4167% a month. The APY (annual percentage yield) is what that does over a whole year once each period's interest starts earning interest of its own.

APY = (1 + APR ÷ n)n − 1
continuous: APY = eAPR − 1
back again: APR = n × ((1 + APY)1/n − 1)

Worked example: 0.05 ÷ 12 = 0.0041667, and 1.004166712 = 1.05116, so 5% APR compounded monthly is an APY of 5.116%. On $10,000 that is $511.62 in a year rather than $500.

US savings accounts quote an APY because the Truth in Savings rules (Regulation DD) require it, worked out as APY = 100 × [(1 + interest ÷ principal)365 ÷ days in term − 1]. Loans and credit cards quote an APR under the Truth in Lending rules (Regulation Z). The same arithmetic runs in reverse on debt: a 22% card APR charged daily grows an unpaid balance by about 24.6% a year.

Sources


More entries in the book

Four more calculators for the interest you earn and the interest you pay.

  1. Simple vs compound interest

    Two balances side by side, year by year, with a growth chart and the gap interest on interest makes.

  2. Credit card payoff calculator

    Months and total interest at a fixed payment, or the payment that clears the card by a set month, with a full schedule.

  3. Minimum payment trap

    What paying only the minimum costs, compared with a fixed payment, and the warning box your statement shows.

  4. Buy now, pay later true cost

    Pay-in-4 and monthly plans with fees and late fees, the yearly rate those fees equal, and a card for comparison.



Questions

Which number should I compare between savings accounts?

The APY. It already includes compounding, so accounts that add interest on different schedules can be compared directly. Comparing two APRs only works when both compound on the same schedule.

Does daily compounding make a big difference?

Less than you might expect at savings rates: 5% APR is 5.116% compounded monthly and 5.127% daily. The gap grows with the rate. At 22% the step from monthly (24.36%) to daily (24.60%) is about a quarter of a point.

What does continuous compounding mean?

Interest added in infinitely small steps. It is the mathematical ceiling for a given APR: APY = e^APR − 1, so 5% continuous gives 5.127%, a hair above daily. You meet it more in finance textbooks than on account statements.

Can an APY be lower than its APR?

No. With compounding once a year the two are equal, and more frequent compounding can only push the APY above the APR. If you see a lower APY than APR, check that both figures describe the same account and the same compounding.