Compound Interest Calculator

See how your money grows with compound interest over time.

See how your money grows when interest compounds on itself over time.

Initial principal

Monthly contribution

Annual interest rate

Years

years

Compounding frequency

Future value

Total contributed

Interest earned

Multiplier

Growth by source

Contributions Interest

Enter your starting amount and a monthly contribution, then press Calculate.

How compound interest works

Compound interest means you earn interest on both your original money and the interest it has already earned. The formula is:

A = P(1 + r/n)^nt + PMT × [ ((1 + r/n)^nt − 1) / (r/n) ]

Example: $10,000 invested at 7% with $200 added monthly becomes about $148,000 after 15 years — of which roughly $54,000 is interest.

Use it to: project savings growth, compare accounts, and understand why starting early makes compounding work in your favor.