Rule of 72 Calculator
Compare an approximate doubling time with the exact annual-compounding calculation.
Example result
- Exact modeled doubling time
- 9.01 years
Assumes a constant positive rate and no contributions, fees or taxes. The approximation is less accurate at very low or high rates.
How to calculate it
Assumes a constant positive rate and no contributions, fees or taxes. The approximation is less accurate at very low or high rates.
Worked example
This is an illustrative scenario, not a market benchmark. Select “Reset to example” to reproduce it in the calculator.
- Effective annual growth rate
- 8 %
Approximate doubling time: 9 years
Rule of 72 FAQ
Why are the two times different?
The rule of 72 is a mental shortcut. The logarithmic result uses the exact constant annual-compounding equation.
What does this calculation leave out?
Assumes a constant positive rate and no contributions, fees or taxes. The approximation is less accurate at very low or high rates.
Are my inputs saved or sent to a server?
Calculations run in your browser. We do not send your inputs or results to our server or analytics. A comparison stays in this tab until it is refreshed. A CSV is saved only when you choose to download it. See our privacy policy for ordinary hosting and optional analytics data.
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