Understanding the Rule of 72: A Simple Guide for Everyone

In the world of finance, there are many formulas and rules that seem complex and intimidating. However, there are also some remarkably simple and useful ones, like the Rule of 72. This rule is a quick, handy formula that helps estimate the number of years it will take for an investment to double in value given a fixed annual rate of interest.

It bridges the gap between high finance and everyday financial planning, making it a valuable tool for anyone looking to understand their investments better.

What is the Rule of 72?

The Rule of 72 is a simple way to determine how long an investment will take to double at a given annual rate of return.

By dividing 72 by the annual rate of return, you can get an approximate number of years it will take for the initial investment to grow 100%.

For example, if you have an investment that yields an 8% annual return, you would divide 72 by 8. The result, 9, represents approximately how many years it will take for your investment to double.

Why is the Rule of 72 Important?

The Rule of 72 is particularly important for personal financial planning. It provides a straightforward method to gauge how investments will grow over time. Understanding this can help individuals make more informed decisions about saving for retirement, investing in stocks, bonds, or other financial instruments, and managing their overall financial strategy.

Here’s why the Rule of 72 can be a crucial tool:

  • Simplicity: It doesn’t require complex calculations or financial knowledge. Anyone can use it quickly to get a rough estimate.
  • Planning: It helps in setting realistic expectations on the growth of investments.
  • Comparative Tool: It can be used to compare the potential returns on different investments, assuming other factors like risk are equivalent.

How Do You Use the Rule of 72?

Using the Rule of 72 is straightforward. Simply divide 72 by your expected rate of return to determine approximately how many years it will take for your investment to double. Here are some scenarios where you might find it useful:

  • Investing in Stocks: If a stock market investment is expected to return 10% annually, dividing 72 by 10 gives you 7.2 years for your investment to double.
  • Retirement Savings: If you’re saving in a retirement account with an average growth rate of 6%, using the Rule of 72 shows it will take about 12 years for your money to double. This can help you understand how your money will grow by the time you retire.
  • Comparing Accounts: When choosing between different savings accounts or investment opportunities, you can use the Rule of 72 to quickly assess which option might grow your money faster.

Practical Examples for Everyday Use

Let’s look at a practical example to illustrate how an ordinary person can use the Rule of 72 in everyday financial decisions:

Imagine you have the option to invest in two different bonds: one offers a 4% return, and the other offers a 6% return. Using the Rule of 72, the bond with a 4% return will take 18 years to double your money (72 / 4 = 18).

On the other hand, the bond with a 6% return will take only 12 years to double your money (72 / 6 = 12). This simple calculation can help you decide which bond might be a better investment for your goals, especially if you have a specific timeframe in mind for your financial goals.


The Rule of 72 is a powerful tool that simplifies the process of financial estimation, making it accessible for everyone, not just finance professionals.

It empowers individuals by helping them plan and understand their financial futures. Whether you’re a seasoned investor or just starting out, incorporating the Rule of 72 into your financial toolkit can provide clarity and direction in your investment journey. Remember, while the Rule of 72 offers a good approximation, it’s always beneficial to consult with financial advisors for more tailored advice.