Finance Tools / Rule of 72 Calculator
Rule of 72 Calculator
Quickly estimate how long it takes an investment to double.
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Rule of 72 Calculator
Quickly estimate how long it takes an investment to double.
Features
- Classic Rule of 72 quick estimate
- Exact compound interest comparison
- Single-input simplicity
- 100% free, no signup
How to Use
Step 1
Enter your expected annual interest rate.
Step 2
Click Calculate Doubling Time.
Step 3
Compare the Rule of 72 estimate to the exact calculation.
About This Tool
Rule of 72 Calculator applies the classic mental-math shortcut for estimating investment doubling time, and also shows the more precise compound-interest calculation for comparison.
Frequently Asked Questions
Why is it called the Rule of 72?
Dividing 72 by an interest rate gives a quick, historically popular mental-math approximation of doubling time.
How accurate is the Rule of 72?
It is quite close for typical interest rates between roughly 6% and 10%, and slightly less precise outside that range, which is why the exact figure is also shown.