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Finance Fundamentals
Compound Interest & Rule of 72 Calculator
Einstein reportedly called compound interest the eighth wonder of the world. Whether or not he actually said that, the math behind it is worth seeing for yourself.
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How To Use This Calculator
Enter a starting amount, a monthly contribution, an interest rate, and how many years you're projecting.
The Rule of 72 is a mental shortcut: divide 72 by your annual interest rate to estimate how many years it takes money to double, no calculator required. This tool shows you both that quick estimate and the actual month-by-month growth curve side by side.
Your Inputs
Growth Over Time
-Final Balance
$0
Total Contributed
$0
Total Growth From Compounding
$0
Rule Of 72 Doubling Time
0.0 yrs
Balance Growth: Contributions vs. Compounding
The Rule of 72 is a close approximation, not an exact formula, it gets slightly less accurate at very high or very low interest rates. This is an educational illustration, not a projection of any specific investment's actual future performance.