The Rule of 72 is a quick and simple technique for estimating one of two things:
- The time it takes for a single amount of money to double with a known interest rate.
- The rate of interest you need to earn for an amount to double within a known time period.
The rule states that an investment or a cost will double when:
[Investment Rate per year as a percent] x [Number of Years] = 72.
When interest is compounded annually, a single amount will double in each of the following situations:
The Rule of 72 indicates than an investment earning 9% per year compounded annually will double in 8 years. The rule also means if you want your money to double in 4 years, you need to find an investment that earns 18% per year compounded annually.
You can confirm the rationality of the Rule of 72 as follows: Find factors on the FV of 1 Table that are close to 2.000. (The factor of 2.000 tells you that the present value of 1.000 had doubled to the future value of 2.000.) When you find a factor close to 2.000, look at the interest rate at the top of the column and look at the number of periods (n) in the far left column of the row containing the factor. Multiply that interest rate times the number of periods and you will get the product 72.
To use the Rule of 72 in order to determine the approximate length of time it will take for your money to double, simply divide 72 by the annual interest rate. For example, if the interest rate earned is 6%, it will take 12 years (72 divided by 6) for your money to double. If you want your money to double every 8 years, you will need to earn an interest rate of 9% (72 divided by 8).
Here’s another way to demonstrate that the Rule of 72 works. Assume you make a single deposit of $1,000 to an account and wish for it to grow to a future value of $2,000 in nine years. What annual interest rate compounded annually will the account have to pay? The Rule of 72 indicates that the rate must be 8% (72 divided by 9 years). Let’s verify the rate with the format we used with the FV Table:
To finish solving the equation, we search only the “n = 9” row of the FV of 1 Table for the FV factor that is closest to 2.000. The factor closest to 2.000 in the row where n = 9 is 1.999 and it is in the column where i = 8%. An investment at 8% per year compounded annually for 9 years will cause the investment to double (8 x 9 = 72).
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FAQs
To use the Rule of 72 in order to determine the approximate length of time it will take for your money to double, simply divide 72 by the annual interest rate. For example, if the interest rate earned is 6%, it will take 12 years (72 divided by 6) for your money to double.
What is the Rule of 72 answer? ›
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.
What is the Rule of 72 for double 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. In this case, 18 years.
Which answer is the correct calculation for the Rule of 72? ›
By using the Rule of 72 formula, your calculation will look like this: 72/6 = 12. This tells you that, at a 6% annual rate of return, you can expect your investment to double in value — to be worth $100,000 — in roughly 12 years.
Is the Rule of 72 a reliable way to estimate doubling time? ›
Key Takeaways
The Rule of 72 is a simplified formula that calculates how long it'll take for an investment to double in value, based on its rate of return. The Rule of 72 applies to compounded interest rates and is reasonably accurate for interest rates that fall in the range of 6% and 10%.
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.
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 do I double my money? ›
The time-tested way to double your money over a reasonable amount of time is to invest in a solid, balanced portfolio that's diversified between blue-chip stocks and investment-grade bonds.
What is the rule of 70 doubling money? ›
The rule of 70 is used to determine the number of years it takes for a variable to double by dividing the number 70 by the variable's growth rate. The rule of 70 is generally used to determine how long it would take for an investment to double given the annual rate of return.
How to double $100,000 in a year? ›
Doubling money would require investment into individual stocks, options, cryptocurrency, or high-risk projects. Individual stock investments carry greater risk than diversification over a basket of stocks such as a sector or an index fund.
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 many years does it take to double your money? ›
Very few investors know how long it takes to double their money. Rule of 72 can be of help. Divide 72 by the expected rate of return and the answer is the number of years required to double your money. For example, if a bond offers 6 percent rate of interest per year, then you will double your money in 12 years.
What are the flaws of Rule of 72? ›
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 the doubling formula? ›
Imagine that we have a population growing at a rate of 4% per year, which is a pretty high rate of growth. By the Rule of 70, we know that the doubling time (dt) is equal to 70 divided by the growth rate (r). That means our formula would look like this: dt = 70 / r.
What is the limitation of Rule 72? ›
Limitations of the Rule of 72
The fact that it presumes a constant rate of return is one of its main drawbacks. It is actually challenging to anticipate how long it will take for a stock to double in value because the rate for return on a given investment might vary over time.
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. The savings category also includes money you will need to realize your future goals.
What is the magic number 72? ›
“In wanting to know of any capital, at a given yearly percentage, in how many years it will double adding the interest to the capital, keep as a rule [the number] 72 in mind, which you will always divide by the interest, and what results, in that many years it will be doubled,” wrote Pacioli.
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.
What is the Rule of 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.
