Whether you want to evaluate offers that promise to "double your money fast" or establish investment goals for your portfolio, a quick-and-dirty method will show you how long it will take to double your money. It's called the Rule of 72 and can be applied to any investment.
How the Rule Works
To use the Rule of 72, divide the number 72 by an investment's expected annual return. The result is the number of years it will take, roughly, to double your money. For example, if the expected annual return of a bank Certificate of Deposit (CD) is 2.35% and you have $1,000 to invest, it will take 72/2.35 or 30.64 years for you to double your original investment to $2,000. If the expected annual return on a CD is 5% and you invest the same amount, it will take you 14.4 years to double your money.
CDs are great for safety and liquidity, but let's look at stocks. It's impossible to know in advance what will happen to stock prices. We know that past performance does not guarantee future returns. But by examining historical data, we can make an educated guess. According to Standard and Poor's, the average annualized return of the S&P index, which later became the S&P 500, from 1926 to 2020 was 10%. At 10%, you could double your initial investment every seven years (72 divided by 10). In a less-risky investment such as bonds, which have averaged a return of about 5% to 6% over the same period, you could expect to double your money in about 12 years (72 divided by 6).
Keep in mind that we're talking about annualized returns or long-term averages. In any given year, stocks might return 25% or lose 30%. Over a long period, the returns will average out to 10%. The Rule of 72 doesn't mean that you'll be able to take your money out of the stock market in 10 years. You might have doubled your money by then, but the market could be down, and you might have to leave your money in for several more years until things turn around. If you must achieve a certain goal or be able to withdraw your money by a certain time, the Rule of 72 isn't enough. You'll have to plan carefully, choose your investments wisely, and keep an eye on your portfolio.
Achieving Your Investment Goals
A professional financial advisor may be your best bet for achieving specific investing goals, but the Rule of 72 can help you get started. If you know that you need to have a certain amount of money by a certain date, for example, for retirement or to pay for your newborn child's college tuition, the Rule of 72 can give you a general idea of which asset classes you'll need to invest in to achieve your goal.
First, you can use the Rule of 72 to determine how much college might cost in 18 years if tuition increases by an average of 4% per year. Divide 72 by 4% and you know that college costs are going to double every 18 years.
Right now you have $1,000 to invest and with an 18-year time horizon, you want to put it all in stocks. We saw in the previous section that investing in the S&P 500 has historically allowed investors to double their money about every six or seven years. Your initial $1,000 investment will grow to $2,000 by year 7, $4,000 by year 14, and $6,000 by year 18. Suddenly 18 years isn't as long a time horizon as you thought, perhaps leading you to rethink your investment strategy.
The Bottom Line
While the Rule of 72 is a good investment guideline, it only provides a framework. If you're looking for a more precise outcome, you'll need to better understand an asset's future value formula. The Rule of 72 also does not take into account the effect of investment fees, such as management fees and trading commissions, can have on your returns. Nor does it account for the losses you'll incur from any taxes you have to pay on your investment gains.
FAQs
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. You would need to earn 10% per year to double your money in a little over seven years.
How can I double my money every 7 years? ›
1 At 10%, you could double your initial investment every seven years (72 divided by 10). In a less-risky investment such as bonds, which have averaged a return of about 5% to 6% over the same period, you could expect to double your money in about 12 years (72 divided by 6).
What is the 7 year money rule? ›
How the Rule of 72 Works. 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 7 year rule for compound interest? ›
When does money double every seven years? To use the Rule of 72 to figure out when your money will double itself, all you need to know is the annual rate of expected return. If this is 10%, then you'll divide 72 by 10 (the expected rate of return) to get 7.2 years.
What is the doubling money trick? ›
There's actually a simple trick that allows you to quickly estimate when you can double your money. It's called the Rule of 72. The principle is simple. Divide 72 by the annual rate of return to figure how long it will take to double your money.
Is the rule of 72 accurate? ›
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.
Does 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.
Do investments really double every 7 years? ›
Assuming long-term market returns stay more or less the same, the Rule of 72 tells us that you should be able to double your money every 7.2 years. So, after 7.2 years have passed, you'll have $200,000; after 14.4 years, $400,000; after 21.6 years, $800,000; and after 28.8 years, $1.6 million.
How long does it take to 10x your money? ›
By saving the right amount and prioritizing growth when your investment time horizon is long, 10x growth is surprisingly attainable over a 20-year period.
What is the Rule of 72 6 years? ›
The Rule of 72 is a way to estimate how long it will take for an investment to double at a given interest rate, assuming a fixed annual rate of interest. You simply take 72 and divide it by the interest rate number. So, if the interest rate is 6%, you would divide 72 by 6 to get 12.
According to his math, since 1949 S&P 500 investments have doubled ten times, or an average of about seven years each time. In some cases, like 1952 to 1955 or 1995 to 1998, the value of the investment doubled in only three years.
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.
Can I double my money in 5 years? ›
As a rate of return, long-term mutual funds can offer rates between 12% and 15% per year. With these mutual funds, it may take between 5 and 6 years to double your money.
What is the magic number to double your 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.
How to double $10,000 fast? ›
Here are some ways to flip $10,000 fast:
- Flip items (buy low, sell high)
- Start a blog.
- Start an online business.
- Write an email newsletter.
- Create online courses or teach online.
- Invest in real estate with EquityMultiple.
For a quick return on a $5,000 investment, consider options like stock trading, especially in high-growth sectors or investing in a diversified mutual fund. Short-term P2P lending can also be a way to see quicker returns, though it carries higher risk.
Is 7% annual return realistic? ›
He said a more reasonable return assumption is 5% for a balanced portfolio of stocks and bonds or 7% for a more aggressive exposure to stocks.
How many years does a sum of money doubles itself in 7 years? ›
CONCEPT: Simple interest concept. Now, we want the money to be quadruple i.e. 4 times. ∴ The money will quadruple itself in 21 years.
Will stocks double in 7 years? ›
A common rule of thumb, the rule of 72, states that you can know how long it'll take for your investment to double by dividing 72 by the rate of return. A 10% annual return means your money should double every 7.2 years. This can be a powerful investment insight, a real-life version of the “grain of rice” folktale.
How many years does it take to double a $100 investment when interest rates are 7 percent per year? ›
It will take a bit over 10 years to double your money at 7% APR. So 72 / 7 = 10.29 years to double the investment.
