The Rule of 72
Divide 72 by your annual return (%). The result is approximately how many years to double your money. Simple and powerful.
What is the Rule of 72?
Years to double = 72 / annual rate (%). At 7% return, 72/7 ≈ 10 years to double. At 6%, about 12 years. It's an approximation derived from compound interest math — not exact, but very close for typical rates.
📊 Use our Rule of 72 Calculator to compute years to double or required rate.
Reverse It
Want to double in 10 years? Required rate = 72/10 = 7.2%. Useful for setting savings or investment goals: "I need about 7% to double in a decade."
When It Works Best
The rule is most accurate for rates between 4% and 15%. Outside that range, the approximation drifts. For precise numbers, use a compound interest calculator.
Why 72?
72 divides evenly by many common rates (6, 8, 9, 12) and comes from ln(2) ≈ 0.693. The exact formula is years = ln(2)/ln(1+r). 72 is just a handy shortcut.
For informational purposes only. Not financial advice.