📈 Compound Interest Calculator

See the power of "Interest on Interest" over time.

Calculate Growth

The 8th Wonder of the World

Albert Einstein reportedly called compound interest the "eighth wonder of the world." Unlike simple interest (where you only earn money on your initial cash), compound interest allows you to earn interest on your interest.

The Rule of 72

A quick mental math trick: Divide 72 by your interest rate to see how many years it takes to double your money.

• At 7% return (Stock Market avg), money doubles every 10.2 years.
• At 1% return (Savings Account), money doubles every 72 years.

Why Start Early?

Time is the most important factor. Investing $500/month starting at age 25 yields significantly more by age 60 than starting at age 35, even if you invest double the amount later. Use the calculator above to see the difference just 10 years makes.