Rule of 72 Calculator
How many years it takes to double your money at a given return, by the Rule of 72 and the exact formula.
Exact years to double
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Rule of 72 estimate—
How to use the Rule of 72 calculator
- Enter annual return.
- Read the exact years to double at the top of the result, with rule of 72 estimate underneath. It updates as you type.
- Change one input at a time to see what moves the answer most, then save the result with Copy link or Download PDF.
About this tool
A quick mental check for any rate: 72 divided by the return gives the doubling time. It is most accurate between 6% and 10%.
Formula: Years ≈ 72 ÷ rate; exact = ln 2 ÷ ln(1 + rate)
Worked example
With annual return of 8%:
| Exact years to double | 9 years |
| Rule of 72 estimate | 9 years |
Built and reviewed by Savitar Finance (savitarfinance@gmail.com). Rules and rates last checked October 2026. How we calculate · Report a problem
Questions people ask
What is the Rule of 72?
Divide 72 by the annual return to estimate years to double. At 8%, money doubles in about 9 years.
Does it work for inflation?
Yes. At 6% inflation, prices double in about 12 years.