Compound Interest Calculator

About Compound Interest Calculator

A compound interest calculator shows how money grows when interest earns interest. Enter a starting amount, annual rate, number of years, how often it compounds, and any regular contributions, and it projects your future balance along with how much you put in versus how much is interest. It updates instantly in your browser.

Frequently asked questions

What is compound interest?

It's interest calculated on both your original amount and the interest already earned. Over time this snowballs, so the balance grows faster the longer you leave it.

Does compounding frequency matter?

Yes. More frequent compounding (monthly or daily vs. annually) earns slightly more, because interest is added and starts earning sooner.

How are regular contributions handled?

Each contribution is added at the end of every compounding period and then earns interest for the remaining time — the standard 'future value of a series' formula.

Is this financial advice?

No. It's a math tool for projections using the numbers you enter; real returns vary and aren't guaranteed.