Rule of 72 Calculator
Divide 72 by an annual rate of return to estimate how many years it takes an investment to double, a quick mental-math shortcut.
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Enter a rate of return to see the years to double.
Worked example
With these example inputs:
- Annual rate of return8%
Years to double: 9
- Rate of return8.0%
- Exact doubling time9.01
- Years to triple14.27
- Years to quadruple18.01
Frequently asked questions
How does the Rule of 72 work?
Divide 72 by the annual percentage rate to approximate the years for money to double. At 8%, money doubles in about nine years.
How accurate is it?
It is a close approximation for rates between roughly 6% and 10%. For very high or low rates it drifts from the exact figure, so treat it as a rule of thumb.