Compound Interest Calculator

A compound interest calculator shows how savings or investments grow when the interest you earn is added to the balance and starts earning interest of its own. Enter a starting amount, a monthly contribution, an annual interest rate and a number of years, and it returns the future value, how much of it you paid in and how much is interest, together with a year-by-year chart and table.

It uses the standard formula A = P(1 + r/n)^(nt), where P is the starting amount, r the annual rate, n the number of compounding periods per year and t the number of years, and it adds every regular contribution with its own growth. You can choose daily, monthly, quarterly, semiannual or annual compounding, decide whether deposits are made at the start or the end of each period, and enter an inflation rate to see the result in today’s money.

Use it to compare savings accounts and certificates of deposit, estimate a retirement or index-fund portfolio, set a target for a child’s education fund, or see how much starting a few years earlier changes the result. The figures are estimates: real returns vary, and taxes and fees are not included.