What is the Rule of 72?

The Rule of 72 is a shortcut: divide 72 by the annual return rate to estimate how many years it takes to double your money. At 8% annual return, money doubles in roughly 9 years.

Rule of 72 Calculator

Estimate doubling time from an annual growth rate.

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About This Calculator

The Rule of 72 is a mental math shortcut: divide 72 by an annual growth rate to estimate how many years it takes for money to double. It's accurate to within a few percent for rates between 2% and 30%, making it one of the most useful quick estimates in personal finance.

Estimates only — not financial, tax, legal, or investment advice. Verify important results with a qualified professional before making decisions.

approximate doubling years ≈ 72 ÷ rate; exact = ln(2) ÷ ln(1 + rate)