Compound Interest Calculator

See how a starting balance grows when interest earns interest — with optional regular contributions added at the end of each compounding period.

Investment details

Starting amount ($)

Annual interest rate (%)

Years

Compounded

Contribution per period ($, optional)

Result

Enter your investment details and press Calculate.

How it works

Each period, interest is added to the balance at the annual rate divided by the number of periods per year, and any contribution is deposited at the period's end. Over long horizons the interest earned on past interest — the compounding — usually outgrows the deposits themselves.