Compound Interest Calculator

Enter your starting amount, interest rate, time period, and optional monthly contributions to see your money grow. Includes a year-by-year breakdown and growth chart.

$144,573
Final Balance
$58,000
Total Contributions
$86,573
Interest Earned
$0$29K$58K$87K$116K$145KYr 1Yr 5Yr 9Yr 13Yr 17Yr 20
Total BalanceContributions

This calculator provides estimates for illustrative purposes only and does not constitute financial advice.

How it works

Compound interest is interest calculated on both the initial principal and the accumulated interest from previous periods. Unlike simple interest, which only grows linearly, compound interest grows exponentially because each period's interest earns interest in subsequent periods. The standard formula is A = P(1 + r/n)^(nt), where P is the principal, r is the annual rate, n is the compounding frequency, and t is the number of years.

When you add regular monthly contributions, the calculator applies the future value of an annuity formula on top of the compound growth of your initial deposit. This shows the powerful effect of consistent saving combined with compounding — even small monthly additions can dramatically increase your final balance over long time horizons.

The year-by-year breakdown table separates your total balance into the amount you contributed and the interest earned, so you can see exactly how much of your wealth comes from your own deposits versus compounding growth. The accompanying chart visualizes this split over time. All calculations are performed in your browser with no data sent to any server.