Rule of 72
Also known as: Doubling Time Rule
t \approx \frac{72}{r}
t ≈ 72 / rWhat It Calculates
A quick mental math shortcut to estimate how many years it takes for an investment to double at a given annual rate of return.
variables
| Symbol | Name | Description |
|---|---|---|
| t | Doubling Time | Approximate years for an investment to double |
| r | Annual Rate | Annual interest rate as a percentage (not decimal) |
Worked Examples
1
t = 72 / 8 = 9 yearsResult: ~9 years
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