Rule of 72 Calculator

Quickly estimate how long it takes to double your money at any interest rate, or what rate you need to achieve your doubling goal.

10.3
Years to Double Your Money
%
10.24
Exact Years (Compound)
10.29
Rule of 72 Estimate
99.5%
Rule Accuracy
Common Interest Rate Doublings
Money Growth Over Time ($10,000 initial)

How the Rule of 72 Works

The Rule of 72 is a quick mental math trick: divide 72 by the interest rate to get the approximate years to double. It's remarkably accurate for rates between 6-10%.

Years to Double ≈ 72 ÷ Interest Rate

For example, at 8% interest: 72 ÷ 8 = 9 years to double. The exact formula using compound interest gives 9.01 years, showing how accurate this simple rule is!

Exact Years = ln(2) ÷ ln(1 + rate) = 0.693 ÷ ln(1 + rate)

Disclaimer: This calculator is provided for educational and informational purposes only. Results are estimates based on the inputs you provide and may contain errors or inaccuracies. This tool does not constitute professional financial, investment, or tax advice. Individual circumstances vary, and you should consult with a qualified financial advisor, accountant, or other professional before making any financial decisions. We make no guarantees regarding the accuracy, completeness, or reliability of the calculations or results provided.

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