APY Calculator

What is an APY calculator?

An APY calculator converts a nominal interest rate into the annual percentage yield — the true rate of return you actually earn once compounding is taken into account. You enter a stated annual rate, choose how often it compounds (monthly, daily, quarterly and so on), and the tool returns the effective APY as a percentage. Add an optional deposit and it also shows the interest earned in year one and the ending balance.

The key idea: a bank might advertise “5%,” but if that 5% compounds monthly, interest gets added to your balance every month and then earns interest itself. By year-end you have earned a little more than a flat 5% — that “little more” is what APY captures. This tool is part of our finance calculators collection and runs entirely in your browser, so nothing you type is sent anywhere.

How is APY calculated?

The calculator uses the standard annual percentage yield formula:

APY = (1 + r ÷ n)^n − 1

The result is a decimal that the tool multiplies by 100 to show as a percent. Where:

• r — the nominal annual interest rate as a decimal (5% = 0.05). The tool accepts a percentage and converts it for you.
• n — the number of compounding periods per year: annually = 1, semi-annually = 2, quarterly = 4, monthly = 12, daily = 365.

More frequent compounding (a larger n) raises the APY above the stated nominal rate, because interest is added — and then itself starts earning — more often during the year. When n = 1, the formula collapses to (1 + r)^1 − 1 = r, so the APY simply equals the nominal rate.

If you enter a deposit, the tool applies the APY to it:

• Interest earned (year one) = deposit × APY
• Ending balance = deposit × (1 + APY)

Units matter: keep r as an annual rate (not monthly), and make sure n matches how the account actually compounds. A monthly rate entered as if it were annual, or the wrong n, is the most common source of error.

Examples

Example 1 — 5% compounded monthly

Here r = 0.05 and n = 12:

APY = (1 + 0.05 ÷ 12)^12 − 1 = 5.1162%

So a stated 5% nominal rate is really a 5.1162% APY when it compounds monthly. On a $10,000 deposit, that is about $511.62 of interest in year one, for an ending balance near $10,511.62.

Example 2 — 5% compounded daily

Same nominal rate, but now n = 365:

APY = (1 + 0.05 ÷ 365)^365 − 1 ≈ 5.1267%

Daily compounding lifts the yield to about 5.1267% APY — higher than the 5.1162% from monthly, but only by roughly a hundredth of a percentage point. On $10,000 that extra precision is worth about a dollar a year.

Example 3 — 4% compounded monthly on a $25,000 deposit

With r = 0.04 and n = 12:

APY = (1 + 0.04 ÷ 12)^12 − 1 ≈ 4.0742%

The effective yield is about 4.0742% APY. On a $25,000 deposit, year-one interest is roughly $1,018.54, ending the year near $26,018.54.

Example 4 — 6% compounded daily on a $5,000 deposit

With r = 0.06 and n = 365:

APY = (1 + 0.06 ÷ 365)^365 − 1 ≈ 6.1831%

A 6% nominal rate compounded daily becomes about 6.1831% APY. On a $5,000 deposit that is roughly $309.16 of interest in the first year, for an ending balance near $5,309.16.

APY reference table

The table below shows how a single 5% nominal rate turns into different APYs as the compounding frequency rises, using the same formula the tool applies. It is a quick way to sanity-check a result.

Compounding	n	APY	Interest on $10,000 (year 1)
Annually	1	5.0000%	$500.00
Semi-annually	2	5.0625%	$506.25
Quarterly	4	5.0945%	$509.45
Monthly	12	5.1162%	$511.62
Daily	365	5.1267%	$512.67

Notice the pattern: moving from annual to monthly adds about 0.12 of a percentage point, but monthly to daily adds barely 0.01. The nominal rate drives almost all of your yield; compounding frequency is a small bonus on top.

Common uses for an APY calculator

• Comparing savings accounts and CDs — banks must quote APY, so this lets you confirm an advertised figure or convert a nominal rate to compare offers fairly.
• Turning APR into APY — translate a stated nominal annual rate into the effective yield you will actually earn (or pay) once compounding is applied.
• Estimating year-one interest — see roughly how much a lump-sum deposit will earn in its first year at a given APY.
• Checking high-yield offers — verify whether a “daily compounding” headline meaningfully beats a monthly-compounding competitor (usually only by a hair).
• Teaching the time value of money — show, with real numbers, why the frequency of compounding matters far less than the rate itself.

Tips and common mistakes

• Enter the rate as a percentage, not a decimal. Type 5, not 0.05 — the tool converts it. The formula above uses the decimal form r.
• Don’t confuse APR with APY. APR is the nominal rate before compounding; APY is the effective yield after. For the same nominal rate, APY is always greater than or equal to APR, and they are equal only when interest compounds once a year.
• Match n to the real account. Daily-compounding accounts use n = 365, monthly use 12. Picking the wrong n shifts the result, even if it is small.
• Don’t expect frequency to make you rich. As the table shows, the jump from monthly to daily compounding adds only about 0.01 of a percentage point — chase a better rate, not a fancier frequency.
• APY is a year-one figure here. The interest and ending balance assume a single year; over multiple years the same APY compounds again, growing the balance further.

Limitations and notes

This calculator assumes a constant nominal rate and a fixed compounding frequency for the year, with no deposits or withdrawals after the initial amount. It does not account for taxes, account fees, promotional-rate expirations, or variable rates — all of which change real-world returns. The interest and ending balance shown are year-one results; multi-year growth requires applying the APY repeatedly. Figures are rounded for display, so tiny differences from a bank statement or a hand calculation are normal. Treat the output as an educational estimate, not a guarantee. Everything runs privately in your browser; no inputs leave your device.

For more money planning, project multi-year growth with the compound interest calculator, work out a monthly target with the savings goal calculator, or, on the borrowing side, size an upfront contribution with the down payment calculator and estimate repayments with the mortgage payment calculator — all in our finance calculators hub.