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A quick mental math shortcut: years to double ≈ 72 / annual rate (%). Accurate near 6-10%.

Very close between ~5% and 12%. At extremes the exact logarithmic formula is better.

Estimate years to double an investment using the Rule of 72 and compare to exact annual compounding.

Years to double (Rule of 72)

≈ 9 years

Exact (annual compound): ≈ 9.01 years

Annual rate (%)

Examples

8% → ≈ 9 years (exact ≈ 9.01)

6% → ≈ 12 years (exact ≈ 11.90)

Related: calculadora-interes-compuesto, calculadora-cagr

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Practical information to understand the result and use this tool correctly.

Estimate years to double an investment using the Rule of 72 and compare to exact annual compounding.

The tool runs directly in the browser for immediate results.

Do I need to sign up?: No. The tool works without an account.
Are my data uploaded?: Compatible operations run locally in the browser.
What is the Rule of 72?: A quick mental math shortcut: years to double ≈ 72 / annual rate (%). Accurate near 6-10%.
How accurate is it?: Very close between ~5% and 12%. At extremes the exact logarithmic formula is better.