The Rule of 72 Formula
Years to Double ≈ 72 ÷ Annual Interest Rate (%)
Example: At an 8% annual return → 72 ÷ 8 = 9 years to double your investment.
Finance 6 min read
Rule of 72 Explained: Calculate Investment Doubling Time
Learn the Rule of 72 shortcut formula to calculate how many years it takes for an investment to double at a given annual interest rate.
Published August 11, 2026
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Basic Math Tools STEM Editorial Team
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Updated: August 11, 2026
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