Compound Interest Calculator
See how a lump sum grows when interest is reinvested. Enter the principal, rate, years and how often interest compounds to get the final amount, interest earned and the effective annual rate.
How to use the Compound Interest Calculator
Enter the principal — the lump sum you start with.
Type the annual interest rate in percent.
Set the time in years and choose the compounding frequency.
Read the final amount, interest earned and the effective annual rate.
Frequently asked questions
How is compound interest calculated?
A = P(1 + r/n)^(n×t), where P is the principal, r is the annual rate as a decimal, n is the number of compounding periods per year and t is the time in years. Interest = A − P.
What is the effective annual rate?
The effective annual rate (EAR) is the real yearly return once compounding is included: EAR = (1 + r/n)^n − 1. It is higher than the nominal rate whenever n is greater than 1.
Is my data safe?
Yes. All calculations run in your browser and no financial figures are transmitted anywhere.