Compound Interest Calculator

See how your investments grow with the power of compound interest. Includes optional monthly contributions.

$
%
$
Final Balance —
Total Contributions —
Total Interest Earned —
Principal + Contributions Interest Earned
— —
Effective Annual Rate —
Rule of 72: Doubling Time —

Growth Over Time

Year-by-Year Growth

Year Balance Contributions Interest

How Compound Interest Works

Compound interest means you earn interest on both your original principal and on accumulated interest. The formula is: A = P(1 + r/n)^(nt) + C × ((1+r/n)^(nt) − 1) / (r/n), where P is the principal, r is the annual interest rate, n is the number of compounding periods per year, t is the number of years, and C is the periodic contribution.

About this Calculator

Compound interest is the eighth wonder of the world — this calculator shows you exactly why. Enter your initial investment, regular contributions, interest rate, and time horizon to see how your money grows exponentially. Visualize the power of compounding and understand why starting early makes such a dramatic difference.

Privacy Note: All calculations are performed locally in your browser. No data is ever sent to a server or third party.

Compound Interest Calculator FAQ

What is compound interest?
Compound interest is interest earned on both your original principal AND previously accumulated interest, causing your balance to grow at an accelerating pace.
How often should interest compound?
Common compounding frequencies include daily, monthly, quarterly, and annually. More frequent compounding yields slightly more growth for the same nominal annual rate.
What is the compound interest formula?
The standard formula is A = P(1 + r/n)^(nt), where P is principal, r is the annual interest rate, n is the number of compounding periods per year, and t is time in years.
How can I maximize compound growth?
Start investing early, contribute regularly, reinvest earnings, choose accounts with competitive rates and more frequent compounding, and avoid early withdrawals.