Compound Interest Calculator

See how your savings can grow over time with this free tool. Type the starting amount, the annual interest rate, how often the interest is added and the number of years. Press Calculate to see the future value and the interest earned. Savers use it to compare accounts and plan long-term goals. Everything runs in your browser, so your numbers never leave your device.

The compound interest formula in plain words

Future value = P x (1 + r / n) to the power of (n x t). Here P is the starting amount, r is the annual interest rate as a decimal, n is how many times per year the interest is added, and t is the number of years. Interest earned is simply the future value minus the starting amount.

Solved example: $1,000 at 5% for 2 years

1. Rate as a decimal: 5% / 100 = 0.05.
2. Compounding once per year (yearly), so n = 1 and t = 2.
3. Future value = $1,000 x (1 + 0.05 / 1) to the power of (1 x 2) = $1,000 x 1.1025 = $1,102.50.
4. Interest earned = $1,102.50 – $1,000 = $102.50.

The $1,000 grows to $1,102.50, so the saver earns $102.50 in interest over the two years.

How to use this calculator

1. Type the starting amount in dollars.
2. Type the annual interest rate as a percent, pick how often interest is added (yearly, monthly and more), then type the number of years.
3. Press Calculate and read the future value, the interest earned and the year-by-year balance.

Limits of this tool

This is an estimate only. It is not financial advice and not a loan offer. It assumes a fixed interest rate, with no extra deposits or withdrawals. Real savings accounts may charge fees, tax the interest or change the rate. Always check the account terms before you decide.

Frequently asked questions

What is compounding?

Compounding means the interest is added to your balance, and the next interest is then worked out on the new, larger balance. Each round builds on the last one, which is why growth speeds up over time.

Why does monthly compounding give more than yearly compounding?

With monthly compounding the interest is added 12 times a year instead of once, so each addition starts earning sooner. With $1,000 at 5% for 2 years, monthly compounding gives about $1,104.94, a little more than the $1,102.50 from yearly compounding.

Is this compound interest calculator free to use?

Yes. It is free, needs no sign-up, and runs fully in your browser.

Can the rate or the number of years be zero?

Yes. A zero rate means the balance never grows, and zero years means no time passes, so the future value equals the starting amount. Negative values are rejected with a clear message.

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