Rule of 72 Calculator
Quickly estimate how many years it takes for your investment to double in value at a given annual interest rate using the mathematical Rule of 72.
How to use the Rule of 72 Calculator
- 1Enter expected annual interest or return rate.
- 2View estimated years required to double your capital.
- 3Or switch to enter target years to determine the required return rate.
How Rule of 72 is Calculated
Divide 72 by the annual interest rate percentage.
The Rule of 72 is an accurate approximation of logarithmic compounding for rates between 4% and 15%.
- 1Years to Double = 72 / 9 = 8.0 years
What affects Rule of 72 results
- Extreme interest rates (for rates above 20%, the Rule of 72 formula becomes less precise).
Frequently Asked Questions
How accurate is the Rule of 72?
For interest rates between 6% and 10%, the Rule of 72 is within a few months of exact mathematical logarithmic calculations.
When should I use the Rule of 69 or 70 instead of 72?
The Rule of 69.3 provides closer accuracy for continuous compounding, while 70 is often preferred for 2-5% interest rates. The Rule of 72 is popular because 72 is divisible by 2, 3, 4, 6, 8, 9, and 12.
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