Compound Interest Calculator

FREE TOOL

See the power of compounding. Enter a starting amount, a rate and a time frame — add monthly deposits to model regular saving.

Starting principal ($)

Annual interest rate (%)

Years

Compounding frequency

Monthly deposit ($)

What is compound interest?

Compound interest is interest earned on both your original money and the interest it has already earned. Over long periods this snowball effect can dramatically increase your savings. The formula is A = P(1 + r/n)^nt, where P is principal, r the annual rate, n the number of compounding periods per year and t the number of years.

Start early — time matters more than the amount.
More frequent compounding means slightly more growth.
Regular monthly deposits accelerate the effect.

Estimates only, assuming a constant rate. Real returns vary.