Rule of 72 Calculator
Use the Rule of 72 to estimate roughly how many years it may take an investment to double, or what annual return might be required to double it within a target time frame.
Estimated years to double
9.0 years
Rate needed to double in target time
8.00%
How to Use
- Enter an annual return rate to estimate doubling time.
- Or enter a target number of years to see the approximate rate needed.
- Review both outputs side by side.
- Use the result as a quick planning shortcut, not a precise forecast.
Frequently Asked Questions
What is the Rule of 72?
It is a simple shortcut that estimates doubling time by dividing 72 by the annual rate of return.
Is it exact?
No. It is a quick estimate that works best around moderate growth rates.
Why use 72?
It is convenient because it divides easily by many common interest rates and gives a reasonable approximation.
Can I use this for debt too?
Yes. It can also estimate how quickly a balance may double when interest works against you.