Compound Interest Calculator

Compounding means you earn interest on your interest. A lump sum P at nominal annual rate r, compounded n times a year for t years, grows to:

Monthly contributions each start their own compounding clock, which is why starting early beats contributing more later: in the chart above, the amber region — money the market added — eventually outgrows the emerald region you contributed.

The projection assumes a constant return and steady contributions. Real investment returns vary year to year, and inflation reduces future purchasing power — a common planning habit is to use a real (inflation-adjusted) return of 4–5% instead of a nominal 7–10%. This is an educational model, not investment advice.