Rule of 72 Calculator
Estimate investment doubling time from return rate.
About this tool
The Rule of 72 is a quick mental-math shortcut for estimating how long an investment takes to double at a given annual return rate \u2014 just divide 72 by the rate. This also shows the more precise doubling time for comparison.
Key Features
- Quick Rule of 72 estimate
- Precise doubling time using logarithms, for comparison
- Works for any positive return rate
How to Use
- Enter the annual return rate you expect.
- Click Calculate Doubling Time.
Benefits
- Quickly compare how different return rates affect growth
- Sanity-check more detailed compound interest calculations
- Understand the power of compounding at a glance
Frequently Asked Questions
It's a close approximation for typical rates (roughly 6\u201310%), usually within a few percent of the precise mathematical answer. For very high or very low rates, the approximation drifts further from the exact figure \u2014 which is why this calculator shows both.
No \u2014 this is a pure math estimate based on the return rate you enter. If you want a 'real' doubling time accounting for inflation, enter your expected after-inflation (real) return rate instead of the nominal rate.