Compound Interest Calculator

Enter a starting amount, a rate, a term and how often interest is added. Add a regular contribution if you make one. You get the final value and the year-by-year table.

%
Final value
?
Total invested
?
Interest earned
?

Year by year

The details that change the answer

  • Compounding frequency matters. The same nominal 5% compounded monthly beats 5% compounded yearly, because each month’s interest starts earning immediately. The difference grows with the term.
  • Contributions are added at the end of each period. That is the conservative convention. Adding them at the start would give a slightly higher figure, and calculators that do so without saying it flatter the result.
  • Interest earned is shown separately from what you put in. Over a long term the interest can exceed the contributions, and seeing the two apart is the point of the exercise.
  • The table shows the crossover. You can read off the year when accumulated interest overtakes accumulated contributions.
  • No inflation, tax or fees. This is gross growth at a fixed rate. Real returns after inflation and charges are lower, sometimes markedly.

The equivalent in Excel

Without contributions it is =amount*(1+rate/n)^(n*years). With them, =FV(rate/n, n*years, -contribution, -amount) does the whole thing, where n is the number of compounding periods a year.