## About This Tool

The online Rule of 72 Calculator is used to calculate how many years it will take for your investment to double at a constant coumpound interest rate by using rule of 72.

## Rule of 72

In finance, the rule of 72 is a quick and easy way to calculate how long it will take you to double your investment.

## Formula

For a constant interest rate, the approximate number of years that it will take for your investment to double is estimated by the following rule of 72 formula:

72 / Interest Rate = Years

For example, if you invested $100 at 4% interest, it will take you about 72/4 = 18 years to double your investment to $200.

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