Rule of 72 Calculator
Estimate how long it takes your money to double at a given rate of return — or the rate needed.
Years for your money to double
9 yrs
At a 8% annual return.
About the rule of 72 calculator
The Rule of 72 is a mental-math shortcut for estimating how long an investment takes to double. Divide 72 by the annual rate of return to get the approximate number of years, or divide 72 by a target number of years to find the return you would need.
It is an approximation that works best for rates between roughly 5% and 12%, and it neatly illustrates how even small differences in return dramatically change how quickly money grows.
Frequently asked questions
How accurate is the Rule of 72?
It is a close approximation for moderate rates of return. For very high or very low rates the estimate drifts slightly from the exact doubling time, but it remains a useful quick check.
Does it work for inflation too?
Yes. Dividing 72 by an inflation rate estimates how long it takes prices to double — a handy way to see how inflation erodes purchasing power over time.
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