The Rule of 72, Doubling Your Money, and Investment Returns (2024)

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The Rule of 72, Doubling Your Money, and Investment Returns (1)

Written by Enoch Omololu, MSc (Econ)

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The Rule of 72 has been around forever and is a very simple way to determine how many years it will take to double your money or the funds invested in your investment portfolio.

If you want a shortcut approach to estimating how compound interest will affect your investment holdings over time, the Rule of 72 is simple enough for the most math-hating individual to utilize.

Literally anyone can crunch the numbers and make financial estimates using the Rule of 72 formula.

How the Rule of 72 Works

To estimate how long it will take you to double your investments, use the formula below:

Time (in years) to double your investment = 72 / r

Where r is the annual interest rate (or expected rate of return) expressed as a whole number.

Example 1: Jake has put $10,000 in an investment that earns 8% per annum. How long will it take him to double his initial investment?

Time required to double funds earning 8% = 72/8 = 9 years

After 9 years, Jake’s initial investment of $10,000 will grow to $20,000.

Using the same scenario above, if we vary the interest rate (rate of return), Jake can expect to double his investment as follows:

  • 3% = 24 years
  • 4% = 18 years
  • 5% = 14.4 years
  • 6% = 12 years
  • 7% = 10.3 years
  • 8% = 9 years
  • 9% = 8 years
  • 10% = 7.2 years, and so on…

The examples above assume we know the expected rate of return.

What if we don’t know that the interest rate (or rate of return) is, but have an investment timeline in mind for when we want our money to double? We can re-arrange the Rule of 72 formula as follows:

Rate of return required to double investment = 72 / length of time

Example 2: Jake has $10,000 at his disposal and wants to double it in 6 years. What is the rate of return required for him to accomplish his goal?

Rate required to double his funds in 6 years = 72/6 years = 12%

Therefore, Jake needs to put his $10,000 in an investment that pays 12% per annum if he’s to have $20,000 in 6 years.

*Note: As interest rates go higher, the Rule of 72 becomes less accurate. However, it remains good enough to get a rough idea of your expected investment horizon.

Final Thoughts

Although the Rule of 72 is not as accurate as using your scientific calculator or spreadsheet, it remains a superb shortcut to mentally estimate how long it takes to double your money while taking compound interest into consideration.

Also Read:

  • How To Buy Stocks in Canada
  • How Much Money You Will Need To Retire Early?
  • Investment Risks All Investors Should Understand
  • 10 Top Strategies For Successful Investing
  • How To Invest in Index Funds Like a Pro
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Editorial Disclaimer: The investing information provided here is for informational purposes only and is not intended as individual investment advice or recommendation to invest in any specific security or investment product. Investors should always conduct their own independent research before making investment decisions or executing investment strategies. Savvy New Canadians does not offer advisory or brokerage services. Note that past investment performance does not guarantee future returns.

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Author

Enoch Omololu, MSc (Econ)

Enoch Omololu, personal finance expert, author, and founder of Savvy New Canadians, has written about money matters for over 10 years. Enoch has an MSc (Econ) degree in Finance and Investment Management from the University of Aberdeen Business School and has completed the Canadian Securities Course. His expertise has been highlighted in major publications like Forbes, Globe and Mail, Business Insider, CBC News, Toronto Star, Financial Post, CTV News, TD Direct Investing, Canadian Securities Exchange, and many others. Enoch is passionate about helping others win with their finances and recently created a practical investing course for beginners. You can read his full author bio.

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FAQs

The Rule of 72, Doubling Your Money, and Investment Returns? ›

All you do is divide 72 by the fixed rate of return to get the number of years it will take for your initial investment to double. For example, if your investment earns 6% per year on average, you would take 72 divided by 6 to determine that it will take 12 years for your money to double.

What is the Rule of 72 answer? ›

For example, the Rule of 72 states that $1 invested at an annual fixed interest rate of 10% would take 7.2 years ((72/10) = 7.2) to grow to $2. In reality, a 10% investment will take 7.3 years to double (1.107.3 = 2). The Rule of 72 is reasonably accurate for low rates of return.

What is the Rule of 72 for doubling money? ›

The Rule of 72 is a calculation that estimates the number of years it takes to double your money at a specified rate of return. If, for example, your account earns 4 percent, divide 72 by 4 to get the number of years it will take for your money to double.

Why is the Rule of 72 useful if the answer will not be exact? ›

The rule of 72 can help you get a rough estimate of how long it will take you to double your money at a fixed annual interest rate. If you have an average rate of return and a current balance, you can project how long your investments will take to double.

What does the Rule of 72 say? ›

Do you know the Rule of 72? It's an easy way to calculate just how long it's going to take for your money to double. Just take the number 72 and divide it by the interest rate you hope to earn. That number gives you the approximate number of years it will take for your investment to double.

Do 90% of millionaires make over $100,000 a year? ›

Choose the right career

And one crucial detail to note: Millionaire status doesn't equal a sky-high salary. “Only 31% averaged $100,000 a year over the course of their career,” the study found, “and one-third never made six figures in any single working year of their career.”

What is the Rule of 72 Quizlet? ›

The number of years it takes for a certain amount to double in value is equal to 72 divided by its annual rate of interest.

Is the Rule of 72 wrong? ›

Errors and Adjustments

The rule of 72 is only an approximation that is accurate for a range of interest rate (from 6% to 10%). Outside that range the error will vary from 2.4% to 14.0%. It turns out that for every three percentage points away from 8% the value 72 could be adjusted by 1.

What is an example of Rule of 72? ›

The Rule of 72 Calculation Example

Suppose an investment earns 6.0% each year. Q. Given the 6.0% rate of return, how many years will it take for the value of the investment to double? If we divide 72 by 6, we can calculate the number of years it would take for the investment to double.

What is the Rule of 72 triple money? ›

The rules of 72 and 115 provide a quick way of seeing the value and speed of compounding. These are short cuts to determine how long it takes compounded money to double and triple. To calculate how long it takes money to double, divide the interest rate into 72. To see how long money triples, divide it into 115.

How to double $2000 dollars in 24 hours? ›

Try Flipping Things

Another way to double your $2,000 in 24 hours is by flipping items. This method involves buying items at a lower price and selling them for a profit. You can start by looking for items that are in high demand or have a high resale value. One popular option is to start a retail arbitrage business.

How to double 1000 dollars? ›

How Can I Double $1000? If your employer offers a dollar-for-dollar match contribution, you can double $1,000 by investing it in your 401(k). Other than that, there's no easy or risk-free way to double $1,000—you can invest the money in individual stocks, but there will be risks involved.

How to double 5000 dollars? ›

To turn $5,000 into more money, explore various investment avenues like the stock market, real estate or a high-yield savings account for lower-risk growth. Investing in a small business or startup could also provide significant returns if the business is successful.

Why is the Rule of 72 accurate? ›

The value 72 is a convenient choice of numerator, since it has many small divisors: 1, 2, 3, 4, 6, 8, 9, and 12. It provides a good approximation for annual compounding, and for compounding at typical rates (from 6% to 10%); the approximations are less accurate at higher interest rates.

Why do investors use the Rule of 72? ›

Using the rule of 72 allows you to have a solid idea of when your investment would double just from the investment rate. Very conveniently, the number 72 divides cleanly into 1, 2, 3, 4, 6, 8, 9 and 12, allowing for a quick and simple division problem instead of your usual compound interest problem.

What is the Rule of 72 assumptions? ›

The rule of 72 is a calculation that estimates how many years it will take an investment to double in value. The calculation is based on the interest rate of the investment and the assumption that the investment's growth remains consistent.

What is the 50 30 20 rule? ›

The 50-30-20 rule recommends putting 50% of your money toward needs, 30% toward wants, and 20% toward savings.

What is the Rule of 72 and 69? ›

Rules of 72, 69.3, and 69

The Rule of 72 states that by dividing 72 by the annual interest rate, you can estimate the number of years required for an investment to double. The Rule of 69.3 is a more accurate formula for higher interest rates and is calculated by dividing 69.3 by the interest rate.

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