Rule Of 72
Calculator
Results
- Years to double (rule of 72)
- 12
- Exact years to double
- 11.895661
- Exact years to triple
- 18.854176
Investing results
| Years to double (rule of 72) | 12 |
| Exact years to double | 11.895661 |
| Exact years to triple | 18.854176 |
formula-map diagram
- Years to double (rule of 72)
- 12
- Exact years to double
- 11.895661
- Exact years to triple
- 18.854176
Investing relationship
Formula
Years to double ≈ 72 ÷ annual rate (%)= 12
Note
This is not investment advice. It is a simplified model: it applies the displayed standard formula to the figures you entered, ignores taxes, fees, currency effects and credit risk, and assumes cash flows arrive exactly as scheduled. Real markets do not behave that way, and past or projected returns do not guarantee future results. Check the assumptions and consult a licensed adviser before acting on any figure.
More in Investing and markets
See all →Frequently asked questions
How does the Rule of 72 estimate doubling time?+
You divide 72 by the annual growth or interest rate (as a whole number, not a decimal) to get an approximate number of years for an investment to double in value. For example, at 8% annual growth, 72 divided by 8 gives roughly 9 years to double.
How accurate is the Rule of 72 compared to the exact calculation?+
It's a close approximation for interest rates roughly between 6% and 10%, with growing error at very low or very high rates. For precise figures, especially outside that range, use the exact logarithmic formula rather than the rule of thumb.
Does the Rule of 72 work for inflation as well as investment growth?+
Yes, the same math applies in reverse — dividing 72 by an inflation rate estimates how many years it takes for purchasing power to be cut in half, which is a common way people use the rule to think about inflation's long-term impact.
Does the Rule of 72 assume compounding or simple growth?+
It assumes compound growth at a constant annual rate; applying it to simple (non-compounding) interest will give an inaccurate doubling estimate, since simple interest grows linearly rather than exponentially.
Can the Rule of 72 be used for negative rates or decline?+
A variant, sometimes called the Rule of 70 or applied the same way, estimates the time for a value to halve under a constant negative growth rate — dividing 72 (or 70) by the rate of decline gives an approximate number of years to lose half the value.