Formula
Years to double is approximately 72 divided by annual return rate. It is a quick mental shortcut, not an exact projection.
Rule of 72 Calculator
Estimate how many years it may take to double at a given annual return rate.
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Use the related tools and guides when the first answer raises the next question.
How the formula works
Rule of 72 estimate = 72 / annual return rate. At 8%, the shortcut gives about 9 years to double.
Example
Compare 6%, 8% and 12%. The shortcut is useful for quick comparisons, but it is not a promise of future investment returns.
Common mistake
The Rule of 72 works best as a rough mental shortcut. Use compound interest or CAGR calculators when contributions, fees or changing values matter.