Rule of 72 Calculator
Estimate how long it will take your money to double based on your annual rate of return.
Common Examples
| Annual Return | Years to Double |
|---|---|
| 4% | 18 years |
| 6% | 12 years |
| 8% | 9 years |
| 10% | 7.2 years |
| 12% | 6 years |
What Is the Rule of 72?
The Rule of 72 is a simple formula used to estimate how long it takes an investment to double in value.
Simply divide 72 by your expected annual rate of return.
For example, if your investment grows by 8% per year, it will take approximately 9 years to double.
How Long Does It Take to Double Your Money?
| Annual Return | Years to Double |
|---|---|
| 2% | 36 years |
| 3% | 24 years |
| 4% | 18 years |
| 5% | 14.4 years |
| 6% | 12 years |
| 7% | 10.3 years |
| 8% | 9 years |
| 9% | 8 years |
| 10% | 7.2 years |
| 12% | 6 years |
| 15% | 4.8 years |
| 20% | 3.6 years |
Rule of 72 vs Exact Formula
The Rule of 72 is a shortcut used by investors to estimate doubling time.
The exact calculation uses logarithms and provides a more precise answer.
For most investment returns, the Rule of 72 is accurate enough and much easier to calculate mentally.
Real Investing Examples
| Annual Return | Doubling Time |
|---|---|
| Inflation (3%) | 24 years |
| Savings Account (4%) | 18 years |
| S&P 500 Historical Average (10%) | 7.2 years |
| Strong Growth Portfolio (15%) | 4.8 years |
Why Compounding Matters
Small differences in annual return can have a massive impact on long-term wealth.
An investment growing at 6% doubles roughly every 12 years, while an investment growing at 12% doubles every 6 years.
Over several decades, this difference can result in dramatically different portfolio values.
Rule of 72 FAQ
The Rule of 72 estimates how many years it takes for an investment to double at a fixed annual return.
It is a close approximation and works best for annual returns between 6% and 10%.
Because the formula uses the number 72 divided by the annual growth rate.
Yes. You can estimate how long it takes prices to double at a given inflation rate.