Calculator
Rule of 72 Calculator
The Rule of 72 is a mental-math shortcut: divide 72 by your annual return rate to estimate the number of years it takes for money to double. It's remarkably accurate for the mid-single-digit to low-double-digit rates most investors encounter.
Frequently asked questions
How does the Rule of 72 work?
Divide 72 by the annual rate of return (as a whole number). At 8% a year, money doubles in roughly 72 ÷ 8 = 9 years. It's an approximation of the exact logarithmic formula.
How accurate is the Rule of 72?
It's most accurate for rates between about 6% and 10%. For very high or very low rates, the exact compound formula diverges from the estimate.
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