The Rule of 72 (with calculator) (2024)

Have you always wanted to be able to do compound interest problems in your head?Perhaps not... but it's a very useful skill to have because it gives you a lightning fast benchmark to determine how good (or not so good) a potential investment is likely to be.

The rule says that to find the number of years required to double your money at a given interest rate, you just divide the interest rate into 72.For example, if you want to know how long it will take to double your money at eight percent interest, divide 8 into 72 and get 9 years.

Y = 72 / r and r = 72 / Y

where Y and r are the years and interest rate, respectively.

Compound Interest Curve

Suppose you invest $100 at a compound interest rate of 10%.The rule of 72 tells you that your money will double every seven years, approximately:

YearsBalance
Now$100
7$200(doubles every
14$400 seven years)
21$800

If you graph these points, you start to see the familiar compound interest curve:

The Rule of 72 (with calculator) (1)

Practice using the Rule of 72

It's good to practice with the rule of 72 to get an intuitive feeling for the way compound interest works.So...

Why Stop at a Double?

There's nothing sacred about doubling your money.You can also get a simple estimate for other growth factors, as this calculator shows:

Why Does the Rule of 72 Work?

If you want to know more, see this explanation of why the rule of 72 works.(Brace yourself, because it's slightly geeked out.)

The Rule of 72 (with calculator) (2024)

FAQs

The Rule of 72 (with calculator)? ›

Calculator Use

What is the Rule of 72 calculator? ›

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.

What is the Rule of 72 as a shortcut method explained by the formula? ›

The Rule of 72 is a simple way to determine how long an investment will take to double given a fixed annual rate of interest. Dividing 72 by the annual rate of return gives investors a rough estimate of how many years it will take for the initial investment to duplicate itself.

Is the Rule of 72 calculated by dividing the interest rate by 72? ›

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.

Is the Rule of 72 is a simple mathematical equation for calculating the money needed for retirement? ›

Simply put, the Rule of 72 offers a quick and straightforward method for investors to estimate the number of years required to double their money at a consistent rate of return. The formula is simple. You divide 72 by your expected annual rate of return.

What is 72 calculator? ›

Use the Rule of 72 to estimate how long it will take to double an investment at a given interest rate. Divide 72 by the interest rate to see how long it will take to double your money on an investment. Alternatively you can calculate what interest rate you need to double your investment within a certain time period.

How do you calculate 72? ›

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.

What is the rule of 72 example? ›

For example, if an investment scheme promises an 8% annual compounded rate of return, it will take approximately nine years (72 / 8 = 9) to double the invested money. Note that a compound annual return of 8% is plugged into this equation as 8, and not 0.08, giving a result of nine years (and not 900).

Does the rule of 72 really work? ›

For higher rates, a larger numerator would be better (e.g., for 20%, using 76 to get 3.8 years would be only about 0.002 off, where using 72 to get 3.6 would be about 0.2 off). This is because, as above, the rule of 72 is only an approximation that is accurate for interest rates from 6% to 10%.

What is the rule of 72 useful in calculating quizlet? ›

dividing 72 by the interest rate will show you how long it will take your money to double.

Does money double every 7 years? ›

Examples of the Rule of 72

Given a 10% annual rate of return, how long will it take for your money to double? Take 72 and divide it by 10 and you get 7.2. This means, at a 10% fixed annual rate of return, your money doubles every 7 years.

How to double $2000 dollars in 24 hours? ›

The Best Ways To Double Money In 24 Hours
  1. Flip Stuff For Profit. ...
  2. Start A Retail Arbitrage Business. ...
  3. Invest In Real Estate. ...
  4. Play Games For Money. ...
  5. Invest In Dividend Stocks & ETFs. ...
  6. Use Crypto Interest Accounts. ...
  7. Start A Side Hustle. ...
  8. Invest In Your 401(k)

What is the rule of 70 calculator? ›

The rule of 70 calculates the years it takes for an investment to double in value. It is calculated by dividing the number 70 by the investment's growth rate. The calculation is commonly used to compare investments with different annual interest rates.

How is Rule 72 calculator? ›

The Rule of 72 is a convenient method to estimate the approximate time for invested capital to double in value. By merely taking the number 72 and dividing it by the rate of return (or interest rate) expected to be earned, the output is the approximate number of years for an investment to double.

How can I 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.

How to double 1000 dollars? ›

Some of the most consistent strategies to double $1,000 include:
  1. Using the money to start a low-cost side hustle.
  2. Starting an online business.
  3. Buying and flipping goods.
  4. Retail arbitrage.

How long will it take to increase a $2200 investment to $10,000 if the interest rate is 6.5 percent? ›

Final answer:

It will take approximately 15.27 years to increase the $2,200 investment to $10,000 at an annual interest rate of 6.5%.

How long will it take $1000 to double at 6 interest? ›

So, if the interest rate is 6%, you would divide 72 by 6 to get 12. This means that the investment will take about 12 years to double with a 6% fixed annual interest rate.

What is rule 72 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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