Rule of 72 Calculator

Estimate how long money takes to double, or what annual return is needed to double within a target period.

Calculation mode

Rule of 72 inputs

Estimate how long it takes money to double, or the return needed to double within a target period.

Annual return

Starting amount

Rule of 72 estimate

9 years

Actual annual compounding

9.01 years

Effective annual return

Doubled amount

$20,000

Multiple timeline

9.01 years

14.27 years

18.01 years

20.91 years

10x

29.92 years

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What the Rule of 72 estimates

The Rule of 72 divides 72 by an annual return to estimate how many years it takes an investment to double. It is a quick mental shortcut, so the page also shows the annual compounding result for comparison.

When to use the reverse calculation

Switch to target years when you already know a doubling deadline. The calculator converts that target into the annual return implied by the Rule of 72, which helps compare savings, index, dividend, or portfolio assumptions.