Skip to content

Finance · free · no sign-up

Compound Interest Calculator

Compound interest means you earn interest on your interest, which is why long-term savings can grow much faster than the money you put in. See how an initial deposit and regular contributions could grow over time.

How it works Report a problem

Compound Interest Calculator

See how time and compounding can multiply your savings exponentially

$0
Future Account Balance
With re-invested earnings
Total Interest
$0
Total Contributions
$0
Yield on Cost
0%
Compounding Journey

Compound interest is interest earning interest — the reason small, early savings outgrow large, late ones. This calculator projects your balance year by year, with or without regular contributions, so you can see the curve for yourself.

How to use this calculator

  • Enter your starting amount.
  • Add the annual interest rate and the number of years.
  • Add a monthly contribution if you plan to keep adding.
  • Press calculate to see the final balance and how much of it is interest.

The two levers that matter most

Rate matters, but time matters more. Starting ten years earlier at the same rate roughly doubles the ending balance in many scenarios. Run the same numbers with two different start dates and the lesson lands instantly.

Frequently asked questions

What is the compound interest formula?
A = P × (1 + r/n)^(n×t), where P is the principal, r the yearly rate, n the number of compounding periods per year and t the years. Regular contributions add their own compounded amounts on top.
How often should interest compound?
Daily compounding grows slightly faster than monthly, which beats yearly. At typical rates the difference is modest; contributions and time dominate.
What is the Rule of 72?
Divide 72 by your yearly rate to estimate the years needed to double your money. At 8%, about 9 years.