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Rule of 72 Calculator FullScreen

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.

Rule of 72 Calculator


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:

R x T = 72


T = Number of Periods, R = Interest Rate as a percentage

Interest rate required to double your investment: R = 72 / T

Number of periods to double your investment: T = 72 / R

Rule of 72 Calculator Example

Certainly! Here's an example of a Rule of 72 calculator that demonstrates how you can estimate the time it takes for an investment to double based on a given interest rate:

Interest Rate Time to Double (in years)
4% 18
6% 12
8% 9

In this example, we have three different interest rates and their corresponding estimated time to double an investment using the Rule of 72.

The Rule of 72 is a simplified formula used to estimate the time it takes for an investment to double, assuming compound interest. To calculate the approximate time to double, you can use the formula: Time to Double = 72 / Interest Rate

For instance, with an interest rate of 4%, it would take approximately 18 years for an investment to double using the Rule of 72.

Similarly, using the same formula, you can estimate the time to double for interest rates of 6% and 8%.

Please note that the Rule of 72 provides a rough approximation and assumes a constant interest rate and compounding frequency. It is not suitable for precise calculations and may not accurately reflect real-world investment scenarios. Additionally, the Rule of 72 should be used cautiously and in conjunction with other financial analysis tools to make informed investment decisions.