Compound Interest Calculator
See how an initial deposit plus regular contributions grow with compound interest.
Future Value
$0
| Total contributions | $0 |
| Total interest earned | $0 |
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How compound interest works
Compound interest is interest earned on both your original money and the interest it has already earned. Over long periods this "interest on interest" effect dramatically accelerates growth.
The base formula is A = P(1 + r/n)nt, where P is the principal, r the annual rate, n the number of compounding periods per year, and t the number of years. This calculator also adds your regular monthly contributions and compounds them too.
Why start early
Because growth compounds, time is the most powerful factor. Starting a few years earlier — even with smaller amounts — often beats starting later with larger deposits.