Enter a starting amount, annual return, number of years, compounding frequency and an optional monthly contribution to see the future value, total deposits, interest earned, effective annual rate and a year-by-year table.
How to use the compound interest calculator
- Enter the starting amount and the expected annual rate.
- Choose how often interest compounds and how many years.
- Add a monthly contribution to see the effect of regular saving.
The power of compounding
With compound interest, each period’s interest is added to the balance, so next period’s interest is calculated on a larger amount. Over long periods the interest can exceed the money you put in. The rule of 72 gives a quick estimate: divide 72 by the annual rate to get the years needed to double (72 ÷ 12% ≈ 6 years).
Real returns
Returns are never guaranteed, and inflation reduces what future money can buy. Subtract the expected inflation rate from the return to estimate growth in today’s money.
Frequently asked questions
What is the formula for compound interest?
A = P × (1 + r/n)^(n×t), where n is the number of compounding periods per year and t is years.
Updated October 2026 · Built and tested by Sharjeel Tahir · How our tools are tested