Rule of 72 Doubling Time
Get a quick approximate doubling period from a positive annual percentage return. Best used for rough mental comparisons near moderate rates.
How to use Rule of 72 Doubling Time
- Enter “Annual return (%) (> 0)”, using the units and limits shown in its label.
- Select Calculate or Process. Review the result and any validation message before copying or downloading available output. Reset clears the result and restores the starting inputs.
Method & assumptions
Approximate doubling years = 72 / annual percentage rate.
Worked example
At 8%, doubling takes approximately 9 years.
Results and projections are informational estimates, not financial, medical, legal, tax, or property advice. Check assumptions, units, rounding, and local requirements independently. Investment illustrations do not guarantee returns. Keep original files and check transformed output before use.
Questions, answered
How accurate is the rule?
It is only an approximation, most useful around 6–10% annual growth. Use logarithms or a growth model for precise planning.
Where does this calculation run?
It runs locally in your browser. Enter plain numbers without currency symbols or thousands separators; use the same currency and measurement units throughout unless a converter explicitly asks for units.