What is the rule of 72?

Years to double ≈ 72 / annual rate (%). So at 6% it takes about 12 years to double.

It's an approximation. The exact formula is ln(2) / ln(1 + r/100) ≈ 69.3/r for small r.

72 has many divisors and works well for typical interest rates (roughly 3%–15%).

Online Rule of 72 Calculator

Estimate years to double your money: 72 divided by annual rate.

Annual rate (%)

What is the rule of 72?: Years to double ≈ 72 / annual rate (%). So at 6% it takes about 12 years to double.
Is it exact?: It's an approximation. The exact formula is ln(2) / ln(1 + r/100) ≈ 69.3/r for small r.
Why 72?: 72 has many divisors and works well for typical interest rates (roughly 3%–15%).

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