Compound Interest Calculator

See how a starting balance and regular contributions grow over time.

Starting amount ($)

Monthly contribution ($)

Annual interest rate (%)

Years invested

Compounding frequency

Balance after the full term

Total contributed$0

Total interest earned$0

How this is calculated

The starting balance compounds at the chosen frequency using A = P(1 + r/n)^(nt). Monthly contributions are added and compounded from the point each one is made, approximated month by month rather than with a single closed-form formula, so the result reflects realistic month-by-month growth rather than a simplified annual estimate.

FAQ

Does this account for inflation?: No — the result is in nominal (today's) dollars. If you want a rough real-terms figure, subtract expected annual inflation from your rate before entering it.
Is a 7% return realistic?: Historical long-run averages for diversified stock portfolios have been cited around that range, but returns vary year to year and aren't guaranteed — this tool is for planning, not a forecast.