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Finance Calculators
Rule of 72 Calculator
Use the Rule of 72 to quickly estimate how many years it takes an investment to double at a given rate of return.
Years to double
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About the Rule of 72 Calculator
The Rule of 72 is a quick mental-math shortcut for estimating how long it takes an investment to double in value at a fixed annual rate of compound interest, without needing a calculator for logarithms.
Formula: Years to Double ≈ 72 ÷ Annual Interest Rate (%)
For example, at 8% annual growth, money doubles in roughly 72 ÷ 8 = 9 years. It's an approximation that works best for rates between about 6% and 10%.
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