📈 APY Calculator
By ToolNimba Finance Team · Reviewed by ToolNimba Editorial Review, personal finance content · Updated 2026-06-19
This calculator gives an estimate only. The APY a bank actually pays can differ because of its exact compounding method, day-count convention, minimum balance rules, promotional or tiered rates, and fees. Rates also change over time. This is not financial advice, confirm the figures with your provider and speak to a qualified adviser before making decisions.
APY (annual percentage yield) is the real rate of return on a deposit once compounding is taken into account. Because interest earns interest, a 5% rate compounded monthly is worth more than a plain 5% paid once a year. Enter the nominal annual rate (the headline or APR figure) and how often it compounds, and this calculator shows the true APY plus the interest a balance would earn in a year.
What is the APY Calculator?
APY answers a simple question: if interest is added back to your balance during the year, what return do you actually end up with? The headline (nominal) rate, sometimes labelled APR on a savings product, ignores that effect. APY captures it. The more often interest compounds (daily rather than monthly, monthly rather than yearly), the more times interest is added back and starts earning interest itself, so the APY edges above the nominal rate.
The formula is APY = (1 + r/n)^n - 1, where r is the nominal annual rate written as a decimal and n is the number of compounding periods per year. For a 5% rate compounded monthly, r = 0.05 and n = 12, giving (1 + 0.05/12)^12 - 1 = 0.051162, or 5.1162%. Compounded daily (n = 365) the same 5% becomes 5.1267%. Compounded just once a year (n = 1) the APY equals the nominal rate exactly, because there is no intra-year compounding to add.
APY matters most when you compare savings accounts, certificates of deposit, or money market accounts. Two accounts can quote the same nominal rate yet pay different amounts if one compounds daily and the other yearly. APY puts them on a single, comparable footing, which is why US banks are required to disclose APY on deposit accounts. Note the mirror term for borrowing is APR: on loans you generally want a low APR, while on savings you want a high APY.
When to use it
- Comparing two savings accounts or CDs that quote different compounding frequencies on a fair, like-for-like basis.
- Converting a quoted nominal rate (or APR) into the effective yield you will actually earn over a year.
- Estimating how much interest a given balance will earn in twelve months at a stated rate.
- Checking whether daily versus monthly compounding makes a meaningful difference on your deposit.
How to use the APY Calculator
- Enter the nominal annual interest rate as a percentage (the headline or APR figure).
- Choose how often the interest compounds, from annually up to daily.
- Optionally enter a starting balance to see the interest and ending balance after one year.
- Read off the APY, the nominal rate, the yearly interest, and the balance after one year.
Formula & method
Worked examples
A savings account quotes a 5% nominal annual rate, compounded monthly.
- Write the rate as a decimal: r = 5 ÷ 100 = 0.05
- Periods per year: n = 12
- r / n = 0.05 ÷ 12 = 0.00416667
- (1 + 0.00416667)^12 = 1.0511619
- APY = 1.0511619 - 1 = 0.0511619 = 5.1162%
Result: APY ≈ 5.1162%, so $10,000 earns about $511.62 in a year, ending at $10,511.62
The same 5% nominal rate, but compounded daily instead of monthly.
- r = 0.05, n = 365
- r / n = 0.05 ÷ 365 = 0.000136986
- (1 + 0.000136986)^365 = 1.0512675
- APY = 1.0512675 - 1 = 0.0512675 = 5.1267%
- On $10,000 the interest is 10,000 x 0.0512675 = $512.67
Result: APY ≈ 5.1267%, about $1.06 more than monthly compounding on $10,000
APY for a 5% nominal rate at different compounding frequencies
| Compounding | Periods per year (n) | APY |
|---|---|---|
| Annually | 1 | 5.0000% |
| Semi-annually | 2 | 5.0625% |
| Quarterly | 4 | 5.0945% |
| Monthly | 12 | 5.1162% |
| Daily | 365 | 5.1267% |
APY by nominal rate, compounded monthly
| Nominal rate | APY (monthly compounding) |
|---|---|
| 2% | 2.0184% |
| 3% | 3.0416% |
| 4% | 4.0742% |
| 5% | 5.1162% |
| 6% | 6.1678% |
Common mistakes to avoid
- Comparing accounts by nominal rate instead of APY. Two accounts can advertise the same headline rate yet pay different amounts because one compounds daily and the other yearly. Always compare by APY, which already folds in the compounding.
- Confusing APY with APR. APY measures what you earn on savings (higher is better) and includes compounding. APR usually measures the cost of borrowing. On deposits the two only match when interest compounds exactly once a year.
- Forgetting that APY assumes the rate stays put. APY projects forward as if the rate and your balance held steady for a full year. A variable rate, a withdrawal, or a promotional rate that expires will all change the real return.
- Ignoring fees and minimum balance rules. Monthly fees or falling below a required minimum can wipe out the interest implied by a high APY. The advertised yield assumes you meet every condition the account sets.
Glossary
- APY
- Annual percentage yield, the effective yearly return on a deposit once compounding is included.
- Nominal rate
- The stated annual interest rate before compounding is accounted for, sometimes shown as APR on a savings product.
- Compounding frequency
- How many times per year interest is calculated and added to the balance (n in the formula).
- APR
- Annual percentage rate, typically the cost of borrowing. On a one-period deposit it equals the APY.
- Effective annual rate
- Another name for APY, the single yearly rate that reflects the actual return after compounding.
Frequently asked questions
What is APY?
APY (annual percentage yield) is the real return on a deposit over a year once compounding is included. Because interest earns interest, the APY is at least as high as the nominal rate, and higher when interest compounds more than once a year.
How do I convert APR to APY?
Use APY = (1 + r/n)^n - 1, where r is the APR as a decimal and n is the number of compounding periods per year. For example a 5% APR compounded monthly gives (1 + 0.05/12)^12 - 1 = 5.1162% APY. This calculator does the conversion for you.
What is the difference between APY and APR?
APR is the nominal annual rate and is most often used for borrowing, where lower is better. APY adds the effect of compounding and is used for savings, where higher is better. They are equal only when interest compounds exactly once per year.
Why is APY higher than the nominal rate?
When interest compounds during the year, each addition starts earning interest itself. Those extra earnings on earlier interest push the effective yield above the nominal rate. The more frequent the compounding, the larger the gap.
Does more frequent compounding make a big difference?
It helps, but with diminishing returns. On a 5% rate, monthly compounding gives 5.1162% and daily gives 5.1267%, a difference of about a hundredth of a percent. The jump from yearly to monthly matters far more than monthly to daily.
Is a higher APY always better for savings?
A higher APY means more interest for the same balance, so all else equal it is better. But check the conditions: fees, minimum balance requirements, and promotional rates that expire can all reduce what you actually earn below the headline APY.
Sources
- Annual Percentage Yield (APY) , Investopedia
- What is the difference between a loan interest rate and the APR? , U.S. Consumer Financial Protection Bureau