# Rule of 72 Calculator

The Rule of 72 is a useful tool used in finance and economics to estimate the number of years it would take to double an investment through interest payments, given a specific interest rate. This rule can also estimate the annual interest rate needed to double an investment in a specified number of years.

Our Calculator will let you perform both of these calculations as follows.

Choose what you would like to calculate:

- 1. The annual interest rate, or
- 2. The number of years.

If you choose (1) please enter the annual interest rate and then click on the 'Calculate' button to see the estimated number of years needed to double your investment.

If you choose (2) please enter the number of years and then click on the 'Calculate' button to see the estimated annual interest rate needed to double your investment.

### Number of Years to Double Investment Chart

## Rule of 72

The Rule of 72 says that to find the number of years needed to double your money at a given interest rate, you just divide 72 by the interest rate. For example, if you want to know how long it will take to double your money at nine percent interest, divide 72 by 9 and get 8 years.

You can use the rule the other way around too if you want to double your money in twelve years, just divide 72 by 12 to find that it will need an interest rate of about 6 percent.

## Rule of 72 Formula

The Rule of 72 Calculator uses the following formulae:

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R x T = 72
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Where:
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T = Number of Periods, R = Interest Rate as a percentage
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Interest rate required to double your investment:
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R = 72 / T
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Number of periods to double your investment:
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T = 72 / R
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