Compound Interest Calculator

See how money grows when earnings are reinvested. The most important calculation in long-term investing.

Final balance

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Total contributions—

Total interest earned—

Growth multiple—

Year-by-year breakdown

Year	Balance	Interest YTD

How it works. Each compounding period, your balance earns (rate / frequency) and contributions are added. The longer the horizon, the more interest itself earns interest — that's the snowball.

The math

Future value with periodic contributions:

FV = P(1 + r/n)^nt + PMT × [((1 + r/n)^nt − 1) / (r/n)]

where P = principal, r = annual rate, n = compounds per year, t = years, PMT = contribution per compounding period.