Compound Interest Calculator
See how savings and investments grow over time with compound interest and regular contributions.
Future value
170,619.05
after 20 years
Starting balance10,000.00
Total contributions60,000.00
Total invested70,000.00
Interest earned100,619.05
Growth multiple2.44×
About the Compound Interest Calculator
Compound interest means you earn returns on your returns. Given a starting balance, a rate, and a time horizon, this calculator shows the future value along with how much of it came from your own contributions versus growth.
Formula
A = P(1 + r/n)^(nt) for the starting balance, plus PMT · [((1 + r/n)^(nt) − 1) / (r/n)] for regular contributions made at the end of each period.
Frequently Asked Questions
Simple interest is calculated only on the original principal. Compound interest is calculated on the principal plus all interest already earned, which is why the curve accelerates rather than staying straight.
More frequent compounding produces slightly more growth, but the effect is small compared to the rate and the time horizon. Going from annual to daily compounding at 7% adds well under half a percent per year.
Dividing 72 by the annual percentage return gives a rough number of years for money to double. At 8%, that is about nine years. It is an approximation, but a good mental shortcut.
No. The result is a nominal figure. To think in today's money, subtract your expected inflation rate from the return rate before entering it — that gives a real, inflation-adjusted result.
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