Compound Interest Calculator

What is Compound Interest?

Compound interest is interest calculated on both the initial principal and the accumulated interest from previous periods. It's often called "interest on interest" and is the mechanism that makes long-term investing so powerful.

The Rule of 72

A quick way to estimate how long it takes to double your money: divide 72 by the annual interest rate. At 8% return, your money doubles in approximately 9 years (72 ÷ 8 = 9).

Why Start Investing Early

Time is the most powerful factor in compound interest. Starting 10 years earlier can result in significantly more wealth than contributing more money later. This calculator lets you experiment with different scenarios to see the impact of time.