APY Calculator
Convert a quoted annual rate into APY and estimate one-year growth.
How to use this APY calculator
- Enter the quoted annual rate
Type the nominal annual interest rate before compounding.
- Set compounding frequency
Enter how many times per year interest compounds (e.g. 12 for monthly, 365 for daily).
- Add an initial deposit
Enter the balance to use for the one-year growth estimate.
- Review estimated APY
Compare the APY with the quoted rate to see the compounding benefit.
- Compare accounts
Run the calculation for different rate-and-frequency combinations to find the best effective yield.
How this APY calculator works
This APY calculator converts a nominal (quoted) annual interest rate into the annual percentage yield by accounting for compounding frequency. APY is the standardized metric required by the Truth in Savings Act for comparing deposit accounts, and it always equals or exceeds the nominal rate because it includes the effect of earning interest on previously credited interest within the year.
APY = (1 + r/n)^n – 1 A savings account quoting 5 % compounded daily (365 times per year): APY = approximately 5.127 %. On a $10,000 deposit, this means you earn about $512.67 in interest over one year instead of the $500 that a simple quoted rate would produce.
The same 5 % nominal rate compounded monthly (12 times per year) instead of daily produces a slightly lower APY. On a $10,000 deposit, the difference in interest earned over one year is small but grows with larger balances and higher rates, which is why APY — not the quoted rate — is the correct comparison metric.
A 5.5 % quoted rate compounded quarterly (4 times per year) results in a higher APY than 5 % compounded daily, because the base rate itself is more influential than compounding frequency at typical savings-account levels. Always compare APY to APY rather than mixing quoted rates with different compounding schedules.
- ✓ The nominal rate remains constant for the full year — variable-rate accounts may produce a different effective yield.
- ✓ No withdrawals or additional deposits occur during the year; APY measures the yield on a static balance.
- ✓ Compounding is assumed to occur at equal intervals throughout the year.
- ✓ Taxes on interest income are not deducted from the APY figure.
- The difference between the nominal rate and APY grows as compounding frequency increases — daily compounding produces a noticeably higher APY than quarterly compounding at the same nominal rate.
- When comparing savings accounts or CDs, always compare APY rather than the quoted rate, since different institutions may compound at different frequencies.
- For very short holding periods, the compounding benefit is minimal; APY is most meaningful for money held for a full year or longer.
- APY disclosure methodology references
- Deposit-account comparison guidance
What is annual percentage yield?
Annual percentage yield is the effective rate of return on a deposit account after accounting for the effect of compounding within the year. When a bank quotes a nominal interest rate, that rate alone does not tell you how much you will actually earn because it ignores the fact that credited interest earns its own interest in subsequent compounding periods. APY corrects for this by expressing the total growth as if it were a single annual rate applied once. The more frequently interest compounds — monthly, daily, or even continuously — the larger the gap between the nominal rate and the APY. For typical savings accounts the difference is modest, often a few basis points, but it becomes more noticeable at higher rates or over longer holding periods. The Truth in Savings Act requires banks to disclose APY precisely so consumers can make apples-to-apples comparisons across institutions that may compound at different frequencies.
Compounding frequency and its practical impact
Compounding frequency determines how often earned interest is credited to your balance and begins earning interest itself. The most common frequencies are daily, monthly, quarterly, and annually. Daily compounding credits interest every day, so your balance grows by a tiny amount each day and the next day's interest is calculated on the new, slightly higher balance. Monthly compounding does the same but only twelve times per year, so there are fewer opportunities for interest-on-interest within the same period. At the rates offered by most savings accounts, the practical difference between daily and monthly compounding is very small — typically a few cents per thousand dollars per year. The gap widens at higher rates, which is why compounding frequency matters more for certificates of deposit or bonds with above-average yields. When comparing accounts, focus on the APY rather than trying to evaluate compounding frequency separately — APY already incorporates the effect.
APY calculator FAQs
Why is APY higher than the quoted rate?
Because APY includes the effect of compounding within the year. Each time interest is credited, the next compounding period earns interest on a slightly larger balance.
Does compounding frequency make a big difference?
At typical savings rates (3–5%), the difference between monthly and daily compounding is usually small relative to the balance. At higher rates or larger balances, the difference becomes more meaningful.
Should I always choose the highest APY account?
APY is the best single comparison metric for deposit accounts, but also consider withdrawal restrictions, minimum balances, fee structures, and local deposit-protection limits.
Is APY the same as APR?
No. APY measures the return earned on deposits. APR measures the cost of borrowing. Both account for compounding but apply to opposite sides of a financial transaction.