✌️ Rule of 72 Calculator
The Rule of 72 is a quick mental shortcut: divide 72 by the yearly return to estimate the years needed to double your money.
Years to double
How the Rule of 72 Calculator works
The calculator shows the rule-of-72 estimate and the exact doubling time from the compound growth formula.
Years to double ≈ 72 ÷ Rate
Exact years = ln(2) ÷ ln(1 + Rate ÷ 100)
Step-by-step calculation
- 1Enter the yearly return.
- 2Divide 72 by the rate.
- 3Compare with the exact doubling time.
Worked example
At 8% a year: 72 ÷ 8 = 9 years. The exact answer is ln 2 ÷ ln 1.08 = 9.01 years.
Rule of 72 Calculator examples
| Yearly return (%) | Years to double |
|---|---|
| 4 | 18 years |
| 6 | 12 years |
| 8 | 9 years |
| 10 | 7.2 years |
| 12 | 6 years |
Other inputs kept at the calculator's default values. Results calculated by this calculator.
Why use a Rule of 72 Calculator?
Quickly estimate how fast money (or prices) double.
Important factors that can affect your results
- Accuracy drops for very high or low rates.
- Returns are not constant.
- Taxes and fees.
Frequently asked questions
How accurate is it?
Very close for rates between about 6% and 10%. For very high rates it becomes less accurate.
Can I use it for inflation?
Yes — at 3% inflation, prices double in about 72 ÷ 3 = 24 years.
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Last reviewed November 2026 · How we build and check our tools · Report a problem