Rule of 72 Calculator
Last updated: 2026-06-25
The Rule of 72 divides 72 by the annual return (%) to estimate the approximate years to double your money. Example: 6% → 72 ÷ 6 = about 12 years.
Conversely, you can find the required return from a target time: required return = 72 ÷ target time.
Input
Time to double your money (Rule of 72)
0 yrs
| Method | Value |
|---|---|
| Rule of 72 (approximation) | |
| Exact calculation (compounding) |
The Rule of 72 is an approximation for a quick sense of scale. It matches best in the 6%–10% range, and actual returns are not guaranteed. Use it for fun.
How to use
- Choose the basis — choose whether to find the doubling time from a return, or the required return from a target time.
- Enter values — enter the annual return (%) or the desired target time (years).
- View results — press "Calculate" to see both the Rule of 72 value and the exact compounding value.
What is the Rule of 72
The Rule of 72 is a tool for quickly estimating, in your head, how long money takes to double with compounding. You compute it as doubling time (years) ≈ 72 ÷ annual return (%). Because it intuitively shows the power of compounding, it is often introduced to new investors.
| Annual return | Rule of 72 | Exact |
|---|---|---|
| 2% | 36.0 yrs | 35.0 yrs |
| 4% | 18.0 yrs | 17.7 yrs |
| 6% | 12.0 yrs | 11.9 yrs |
| 8% | 9.0 yrs | 9.0 yrs |
| 10% | 7.2 yrs | 7.3 yrs |
| 12% | 6.0 yrs | 6.1 yrs |
As the table shows, the Rule of 72 nearly matches the exact calculation (ln(2) ÷ ln(1+return)) in the 6%–10% range. At very high or low returns, the error grows. For the actual future value of regular investing, use the Compound Interest Calculator, and for ROI and tax basics, see the investing guide.
Frequently asked questions (FAQ)
What is the Rule of 72?
The Rule of 72 is a simple formula to estimate how long it takes for money to double with compounding. Divide 72 by the annual return (%) to get the approximate number of years to double. For example, at a 6% annual return, 72 ÷ 6 = about 12 years.
Is the Rule of 72 accurate?
The Rule of 72 is an approximation. The exact doubling time is ln(2) ÷ ln(1+return), and the Rule of 72 matches reality best in the 6%–10% range. At very high or low returns the error grows, so use it for a quick sense of scale.
How do I find the required return?
To double your money within a target time, divide 72 by the target time (years) to get the required annual return (%). For example, to double in 10 years you need 72 ÷ 10 = about 7.2% annually.
What are the Rule of 114 and Rule of 70?
To estimate the time to triple your money, divide 114 (or 115) by the return. And under continuous compounding, 69–70 is sometimes used instead of 72. For everyday investing, the easy-to-compute Rule of 72 is the most widely used.
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Last updated: 2026-06-25