Compound Interest Calculator

A = P(1 + r/n)^(nt), where P is principal, r is the annual interest rate, n is the number of times interest compounds per year, and t is the number of years. This calculator also adds the future value of any regular monthly contributions.

Simple interest is earned only on the original principal. Compound interest is earned on the principal plus all previously accumulated interest, which is why it grows faster over time — this is often called 'interest on interest.'

It has a real but modest effect. Daily compounding produces slightly more growth than monthly, which produces slightly more than annual, at the same stated rate — the difference grows larger with bigger balances and longer time horizons.