Free compound interest calculator. Calculate how much your investment will grow with compound interest. Compare with simple interest, view year-by-year breakdown, and discover the power of compounding.
This compound interest calculator helps you estimate how much your investment will grow over time. Enter your principal amount, interest rate, time period, and compounding frequency to see the power of compound interest. All calculations happen in your browser — no data is sent to any server.
Compound interest is interest calculated on the initial principal plus all accumulated interest from previous periods. Unlike simple interest, you earn interest on your interest, leading to exponential growth over time.
More frequent compounding leads to higher returns. For example, daily compounding yields more than monthly compounding at the same annual rate because interest is added to the principal more often.
Simple interest is calculated only on the original principal amount. Compound interest is calculated on the principal plus accumulated interest. Over time, compound interest significantly outperforms simple interest.
The Rule of 72 is a quick way to estimate how long it takes to double your money: divide 72 by your interest rate. For example, at 7.2% interest, your money doubles in about 10 years.