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Calculate how your money grows with compound interest. Enter principal, rate, time, and optional monthly contributions to see your future balance.
Calculate compound interest and see how your money grows over time — no signup, no ads. Enter your starting amount, interest rate, time period, and optional monthly contributions. The calculator shows your future balance, total interest earned, and total contributions. Understand the power of compound interest with clear, instant results. Everything runs in your browser.
Compound interest is interest calculated on both the initial principal and the accumulated interest from previous periods. Unlike simple interest (calculated only on the principal), compound interest grows exponentially over time. This is why it's called "the eighth wonder of the world."
The calculator lets you choose: annually (1x/year), semi-annually (2x), quarterly (4x), monthly (12x), or daily (365x). More frequent compounding produces slightly higher returns. Most savings accounts compound daily; most investments compound annually.
Yes. You can add a monthly contribution amount to see how regular investing accelerates growth. This models a systematic investment plan like a 401(k) or regular savings.
The Rule of 72 estimates how long it takes to double your money: divide 72 by the annual interest rate. At 8% interest, money doubles in about 9 years (72/8=9). It's a good approximation for rates between 4-12%.