Compound Interest Calculator

Calculate how an investment grows with compound interest, optional recurring contributions, and custom compounding periods.

How to use the Compound Interest Calculator

  1. Enter your initial investment, annual interest rate, and duration.
  2. Choose how often interest compounds — monthly is typical for savings accounts.
  3. Add a monthly contribution to model regular deposits.
  4. Click Calculate to see the year-by-year growth table.

What is compound interest?

Compound interest means you earn interest on your interest. Over time, this creates exponential growth. The formula is A = P(1 + r/n)^(nt) where P is principal, r is annual rate, n is compounding frequency, and t is time in years.

With regular contributions, each deposit also compounds, which is why starting early makes such a large difference.