Rule of 72 doubling estimate
Estimate doubling time as 72 divided by an annual percentage growth rate.
How this works
Approximate doubling time in years = 72/R, where R is the positive annual percentage growth rate, such as 6 for 6%. The comparison uses exact annual compounding: years = ln(2)/ln(1 + R/100). Both assume a constant rate and no added or withdrawn money.
Example
The illustration may use different inputs from the reproducible default inputs listed below.
At a 6% assumed annual rate, 72/6 = 12 years. The exact annual-compounding comparison is ln(2)/ln(1.06). With all reset-default inputs, approximate years to double: 12.
- Positive annual growth rate (%)
- 6
- Approximate years to double
- 12
Scope and assumptions
The Rule of 72 is an approximation and can differ substantially from the exact calculation, especially outside moderate rates. Fees, taxes, losses and variable returns are excluded. Neither result guarantees that money will double.
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