finance
Rule of 72 Calculator
Estimate how long it takes to double your money at a given return.
%
Years to double (Rule of 72)
9
A quick estimate: 72 divided by the annual rate.
Rule of 72 estimate
9 yrs
Exact doubling time
9.01 yrs
How it works
- 1Enter an annual return or interest rate.
- 2See the Rule of 72 estimate (72 ÷ rate).
- 3Compare it with the exact doubling time.
Use cases
- Quickly gauge how fast an investment grows.
- Compare the impact of different return rates.
- Teach or learn the rule-of-72 shortcut.
Frequently asked questions
What is the Rule of 72?
A shortcut for estimating how long an investment takes to double: divide 72 by the annual percentage rate. At 8% it is about 72 ÷ 8 = 9 years.
How accurate is it?
It is a close estimate for typical rates (roughly 6–10%). This tool also shows the exact doubling time using logarithms for comparison.
Is my data stored?
No. Everything runs in your browser.
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