Compound Interest Calculator

Compound interest is the interest calculated on the initial principal and also on the accumulated interest from previous periods. It makes your money grow faster than simple interest, because you earn returns on your returns. This effect accelerates over time – which is why it's often called the “eighth wonder of the world.”

The standard formula is: A = P (1 + r/n)^(nt) + PMT × [((1 + r/n)^(nt) - 1) / (r/n)], where P is the initial principal, r the annual interest rate, n the number of compounding periods per year, t the number of years, and PMT the periodic contribution (adjusted to the compounding period). Our tool translates monthly contributions into an equivalent monthly rate to give you a realistic projection.

The more frequently interest is compounded, the higher the final amount. For example, daily compounding yields slightly more than monthly, and much more than annual compounding, assuming the same nominal rate. This is because each compounding event adds earned interest to the principal sooner, generating additional interest in future periods.

Yes! It can estimate how your retirement savings could grow with regular contributions. Adjust the monthly contribution to match your planned savings rate and use a realistic annual return (many planners assume 6–8% for stock market returns). Remember, actual returns can vary, and this tool provides estimates, not guarantees.

You can set the initial investment to $0. The calculator will show how consistent monthly investing can build wealth over time. Even small amounts, when compounded, can grow significantly, illustrating the power of discipline and time.