Compound Interest Calculator

See how your money grows over time with compound interest and regular contributions.

How to use

  • Enter your starting principal — the initial amount you're investing.
  • Set the annual interest rate (e.g., 7% for a stock market index fund average).
  • Choose how often interest compounds — daily and monthly are most common.
  • Set the number of years you plan to invest.
  • Add a monthly contribution to see the power of regular investing.
  • The Rule of 72 shows roughly how many years it takes to double your money.