Free tool

Compound interest calculator

What savings grow to with a monthly contribution, and how much of the result is your own money rather than interest.

Updated September 8, 2026

What will it grow to?

After that timeResult
Balance
You put in
Interest earned

The rate matters more than it looks

Cash sitting in a current account earning almost nothing is the most common version of this. The difference between 0.1% and 4% does not sound like much for one year, but it compounds: the gap widens every year because the interest itself starts earning.

The line showing what you put in is the honest one. Over short periods almost all of the balance is your own deposits, and the interest only starts to dominate after a decade or more.

What this leaves out

It compounds monthly and assumes the rate holds for the whole period, which no savings rate does. Tax on interest is not deducted, and inflation is not taken off, so the balance is in future dollars rather than today's buying power. It is arithmetic on the numbers you enter, not a forecast, and it is not investment advice.