Rule of 72 - Double Your Money with Compound Interest

Rule of 72 -  Double Your Money with Compound Interest

The Rule of 72 is a quick way to estimate the years it will take for an investment to double in value, given a fixed annual rate of return. To use the Rule of 72, divide the number 72 by the annual rate of return. For example, if an investment is expected to grow at a rate of 8% per year, it will take approximately nine years to double (72 / 8 = 9).


The Rule of 72 is a valuable tool for understanding the concept of compound interest and how it can help an investment grow over time. It's important to note, however, that the Rule of 72 is only an estimate, and the actual time it takes for an investment to double in value may be different depending on a variety of factors, such as changes in the rate of return or the impact of fees and taxes.


Here are a few examples of how to use the Rule of 72:


  • If an investment is expected to grow at a rate of 6% per year, it will take approximately 12 years for the investment to double (72 / 6 = 12).

  • If an investment is expected to grow at a rate of 9% per year, it will take approximately 8 years for the investment to double (72 / 9 = 8).

  • If an investment is expected to grow at a rate of 12% per year, it will take approximately 6 years for the investment to double (72 / 12 = 6).


The Rule of 72 can be used to estimate how long it will take for a company's earnings per share (EPS) to double, given a fixed annual growth rate. To use the Rule of 72 with EPS growth, divide the number 72 by the annual EPS growth rate.


For example, if a company's EPS is expected to grow at a rate of 8% per year, it will take approximately 9 years for the EPS to double (72 / 8 = 9).


It's important to note that the Rule of 72 is only an estimate, and the actual time it takes for EPS to double may be different depending on a variety of factors, such as changes in the growth rate or the impact of external events on the company's performance. Additionally, the Rule of 72 assumes that the EPS growth rate remains constant, which may not always be the case in the real world. Therefore, it's important to carefully consider all of the factors that may affect a company's EPS growth when making investment decisions.


The Rule of 72 is a useful tool for understanding the concept of compound interest and how it can help an investment grow over time. It can be used in a variety of situations, such as:


  • Estimating how long it will take for an investment to double in value, given a fixed annual rate of return.


  • Understanding the relationship between the rate of return and the time it takes for an investment to grow.

  • Comparing the potential growth of different investments with different rates of return.

  • Planning for long-term financial goals, such as retirement savings or funding a child's education.


Keep in mind that the Rule of 72 is only an estimate, and the actual time it takes for an investment to grow may vary depending on various factors. It's important to consider all of the relevant information when making investment decisions rather than relying solely on the Rule of 72.



Deepak Sharma

Deepak Sharma

Insurance Advisor / WealthGuard


  • My goal is simple, protect what is important to you. I focus my energy on discovering your exposure to risk and building a comprehensive plan to protect you against those risk.