How to use this APY calculator
- Choose Enter rate or From earnings (not both at once).
- In rate mode, enter nominal APR or APY and compounding frequency.
- Select how often interest compounds (daily through annual). High-yield savings often compound daily; many loans accrue monthly—see the amortization schedule for each period’s split.
- Read the converted APY and matching nominal rate.
- Click a row in the comparison table to sync the frequency dropdown; use → to open compound interest with that frequency.
- Optionally enter a deposit to estimate simple one-year interest at the APY. For a target balance or multi-year deposits, try the savings goal calculator or compound interest calculator.
- In earnings mode, enter principal, interest, and days to derive APY and implied nominal APR (frequency sets the APR mapping).
- Copy link to share your inputs in the URL.
APY from interest earned
When you know how much interest you earned over a fixed period, APY ≈ (1 + I/P)365/D − 1, where P is principal, I is interest, and D is days. This matches common U.S. savings disclosure math; it assumes the rate scales to a 365-day year.
Example: 6% APR compounded monthly
With r = 0.06 and n = 12, APY = (1 + 0.06/12)^12 − 1 ≈ 6.17%. That is the standard textbook check for an APY calculator—use the compound interest calculator to see how that yield grows a balance over many years.
APY formula
APY = (1 + r/n)n − 1
Reverse: nominal APR r = n × ((1 + APY)1/n − 1). These assume a constant rate and fixed compounding interval.
APR vs APY at the same nominal rate
Both investments below quote 5% APR, but compounding frequency changes APY: semi-annual compounding gives about 5.0625% APY; monthly gives about 5.1164% APY. The nominal APR is the same; APY shows the effective yield.
APY on savings vs APR on loans
Savings accounts and CDs advertise APY so you can compare effective yield after compounding. Loan contracts usually quote nominal APR and build a payoff schedule where interest accrues on the remaining balance each period—the disclosure is not the same as a savings APY headline. Use the loan calculator for payment and total interest, the amortization schedule for period-by-period principal and interest, and the mortgage calculator for home price, down payment, and optional taxes. To project growing savings with regular deposits, use the compound interest calculator.
Frequently asked questions
What is APY?
APY (annual percentage yield) is the effective yearly return after compounding. It reflects interest earned on both principal and interest already added.
What is the difference between APY and APR?
APR is the nominal annual rate before compounding is expressed as a single yield. APY includes how often interest compounds, so APY is usually slightly higher than APR when compounding is more than once per year. Multi-year growth at a fixed rate is modeled on our compound interest calculator.
How do I calculate APY from APR?
APY = (1 + r/n)^n − 1, where r is the nominal APR as a decimal and n is compounding periods per year.
Does daily compounding give a much higher APY than monthly?
Daily compounding raises APY only slightly compared with monthly at typical savings rates. The gap grows at higher rates or when you compare very different frequencies.
Can I convert APY back to a nominal rate?
Yes. Nominal rate = n × ((1 + APY)^(1/n) − 1) for the same compounding frequency n. Use the APY input mode in the calculator above.
Why might my bank APY differ slightly?
Institutions may use 360-day years, tiered balances, fees, rounding each period, or promotional rates. This page is a planning estimate.
How is one-year interest estimated on this page?
If you enter an optional deposit, we multiply principal × APY for a simple one-year interest estimate. It does not model month-by-month compounding of new deposits. For interest that never compounds into the balance, see the simple interest calculator.
When should I use the compound interest calculator?
Use the compound interest calculator for multi-year balances, regular deposits or withdrawals, inflation, tax, and year-by-month schedules.
How do I estimate APY from interest earned over a period?
Enter principal, interest earned, and days in the earnings section. We use (1 + I/P)365/D − 1 and ignore the APR/APY fields until you clear those earnings inputs.
Can I share my APY calculator inputs?
Copy link saves your settings in the page URL for bookmarking or sharing.
How does the APY comparison table work?
Rows show APY at the same nominal rate for each frequency. Click a row to update the dropdown; the arrow opens compound interest with that frequency pre-filled.
How does APY relate to loan or mortgage calculators?
This page converts nominal rates to effective APY for savings-style compounding. Loan tools model paying down debt with the same math on each remaining balance—start with the loan calculator, amortization schedule, or mortgage calculator.