What are the assumptions of the rule of 72?

Asked by: Prof. Dallas Prosacco PhD  |  Last update: September 13, 2025
Score: 4.5/5 (48 votes)

This formula relies on the fact that the interest rate is equal to the return on investment (ROI). It assumes that no other payments will be made. The interest rate will be fixed and it will be annually compounded. Originally, the rule of 72 was derived from a formula that looks at the logarithms of numbers.

What is the Rule of 72 in simple terms?

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.

How long would it take for you to double your money from $9000 to $20,000 if you will earn 12% interest?

The rule is this: 72 divided by the interest rate number equals the number of years for the investment to double in size. For example, if the interest rate is 12%, you would divide 72 by 12 to get 6. This means that the investment will take about 6 years to double with a 12% fixed annual interest rate.

Does the Rule of 72 always work?

The Rule of 72 is an estimate, and more accurate at around 8 percent interest. The further the interest rate or inflation rate is from 8 percent, the less precise the result will be.

Which of the following is necessary to use the Rule of 72?

All you need to use the tool is an interest rate, which means you can make estimates for your current account rate or use this rule to know what rate you should look for if you want to double your money by a specific deadline.

What Is The Rule Of 72

17 related questions found

What is a situation in which you would use the Rule of 72?

72 ÷ number of years in which you want the investment to double = targeted annual rate of return. For instance, if you know you want your money to double in 6 years, the rule of 72 would have you looking for an investment with an annual rate of return of around 12% (72÷6=12).

How can I double $5000 dollars in a year?

10+ Ways to Double $5,000
  1. Start a Side Hustle. Perhaps the most common method of making more money is starting a side hustle. ...
  2. Invest in Stocks and Bonds. ...
  3. Day Trade. ...
  4. Save More Money. ...
  5. Buy and Resell Items on Amazon and eBay. ...
  6. Build an eCommerce Business. ...
  7. Sell Your Stuff. ...
  8. Earn cashback When You Shop.

What are the flaws of the Rule of 72?

However, the Rule of 72 is based on a few assumptions that may not always be accurate, such as a constant rate of return and compounding period. It also does not take into account taxes, inflation, and other factors that may impact investment returns.

How to double your money in 3 years?

To answer the question of how to double my money quickly, simply invest in a portfolio of investment options like ULIPs, mutual funds, stocks, real estate, corporate bonds, Gold ETFs, National Savings Certificate, and tax-free bonds, to name a few.

What is the $1 rule?

Before buying an item, figure out how many times you'll use it. If it breaks down to $1 or less per use, I give myself the green light to buy it.

Can I live off interest on a million dollars?

Yes, it's possible to retire on $1 million today. In fact, with careful planning and a solid investment strategy, you could possibly live off the returns from a $1 million nest egg.

Does your money double every 7 years?

The Rule of 72 is a simple way to estimate how long it will take your investments to double by dividing 72 by your expected annual return rate. Higher-risk investments like stocks have historically doubled money faster (around seven years) compared with lower-risk options like bonds (around 12 years).

How long in years will it take a $300 investment to be worth $800 if it is continuously compounded at 12% per year?

Thus, it will take approximately 8.17 years.

How to double your money using the Rule of 72?

Here's how the Rule of 72 works. You take the number 72 and divide it by the investment's projected annual return. The result is the number of years, approximately, it'll take for your money to double.

Is there a way to invest without losing money?

The Bottom Line. Safe assets such as U.S. Treasury securities, high-yield savings accounts, money market funds, and certain types of bonds and annuities offer a lower risk investment option for those prioritizing capital preservation and steady, albeit generally lower, returns.

What is rule 69 in finance?

The Rule of 69 is a simple calculation to estimate the time needed for an investment to double if you know the interest rate and if the interest is compounded. For example, if a real estate investor earns twenty percent on an investment, they divide 69 by the 20 percent return and add 0.35 to the result.

How to turn 100k into 1 million?

4 Good Investment Choices for Turning $100k into $1 Million
  1. Real Estate. Real estate remains a solid option for those wondering how to invest 100k to make $1 million in 10 years or less. ...
  2. Stock Market. ...
  3. Index Funds or ETFs. ...
  4. Buying Established Businesses/Websites.

How can I double my money legally fast?

5 ways you can double your money
  1. Get a 401(k) match. Talk about the easiest money you've ever made! ...
  2. Invest in an S&P 500 index fund. An index fund based on the S&P 500 is one of the more attractive ways to double your money. ...
  3. Buy a home. ...
  4. Trade cryptocurrency. ...
  5. Trade options.

What is 1 doubled every day for 30 days?

If you start with 1 dollar and double it every day for 30 days, you would have approximately $1,073,741,824. This shows the concept of exponential growth. Like the penny example, this is not typically possible in real-world investing scenarios.

What did Einstein say about the Rule of 72?

Einstein also said that “If people really understood the Rule of 72 they would never put their money in banks.” Suppose that a 10-year-old has $500 to invest. She puts it in her savings account that has a 1.75% annual interest rate.

What is the 8 4 3 rule of compounding?

As per this thumb rule, the first 8 years is a period where money grows steadily, the next 4 years is where it accelerates and the next 3 years is where the snowball effect takes place.

What is the 73 rule?

IRAs: The RMD rules require individuals to take withdrawals from their IRAs (including SIMPLE IRAs and SEP IRAs) every year once they reach age 72 (73 if the account owner reaches age 72 in 2023 or later), even if they're still employed.

How to turn $5000 into $10000 quickly?

10 Clever Ways To Turn $5,000 Into $10,000
  1. Invest in an index fund. Rido/Adobe. ...
  2. Sell handmade crafts. Grigoriy/Adobe. ...
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  5. Max out an employee-matched retirement account. ...
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  8. Resell discounted items.

Does a 401k double every 7 years?

One of those tools is known as the Rule 72. For example, let's say you have saved $50,000 and your 401(k) holdings historically has a rate of return of 8%. 72 divided by 8 equals 9 years until your investment is estimated to double to $100,000.

How to turn $100 dollars into $1,000 in a month?

10 best ways to turn $100 into $1,000
  1. Opening a high-yield savings account. ...
  2. Investing in stocks, bonds, crypto, and real estate. ...
  3. Online selling. ...
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  5. Opening a Roth IRA. ...
  6. Freelancing and other side hustles. ...
  7. Affiliate marketing and promotion. ...
  8. Online teaching.