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
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).
Will my money double in 7 years? ›
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.
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.
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.
Does the S&P 500 double every 7 years? ›
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.
What is the 7% rule in stocks? ›
However, if the stock falls 7% or more below the entry, it triggers the 7% sell rule. It is time to exit the position before it does further damage. That way, investors can still be in the game for future opportunities by preserving capital. The deeper a stock falls, the harder it is to get back to break-even.
Is a 7% return realistic? ›
While quite a few personal finance pundits have suggested that a stock investor can expect a 12% annual return, when you incorporate the impact of volatility and inflation, 7% is a more accurate historical estimate for an aggressive investor (someone primarily invested in stocks), and 5% would be more appropriate for ...
How to double cash? ›
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 7.2 year rule? ›
Using the Rule of 72, you can realize the power of compounding interest and better plan for future financial goals. If $5,000 was invested with an annual growth rate of 10%, the original investment would double to $10,000 in 7.2 years. After 7.2 years $10,000 doubles to $20,000.
What will 50k be worth in 20 years? ›
Assuming an annual return rate of 7%, investing $50,000 for 20 years can lead to a substantial increase in wealth. If you invest the money in a diversified portfolio of stocks, bonds, and other securities, you could potentially earn a return of $159,411.11 after 20 years.
“By the time you hit 33 years old, you should have $100,000 saved somewhere,” he said, urging viewers that they can accomplish this goal. “Save 20 percent of your paycheck and let the market grow at 5% to 7% per year,” O'Leary said in the video.
How much is a 401k worth in 20 years? ›
As a very basic example, if you had $5,000 in your 401(k) today, and it grew at an average rate of 5% per year, it would be worth $10,441 in 20 years—more than double. If you withdraw those funds early, however, you're not only facing a stiff tax penalty, you're losing all of that additional growth.
How to turn 100k into 1 million? ›
If you keep saving, you can get there even faster. If you invest just $500 per month into the fund on top of the initial $100,000, you'll get there in less than 20 years on average. Adding $1,000 per month will get you to $1 million within 17 years. There are a lot of great S&P 500 index funds.
How to turn 50k into 100k? ›
One way to turn 50k into 100k is by strategically investing in real estate opportunities. One popular real estate investment strategy is purchasing rental properties. By buying a property and renting it out, you can generate a steady stream of passive income.
How to get 10% return on investment? ›
Investments That Can Potentially Return 10% or More
- Stocks.
- Real Estate.
- Private Credit.
- Junk Bonds.
- Index Funds.
- Buying a Business.
- High-End Art or Other Collectables.
nm97 wrote: A sum of money doubles itself in 7 years. In how many years it becomes four fold? If the initial amount of money is x dollars, then 7 years later, it will be 2x dollars, and in another 7 years, it will be 4x dollars. Thus, it takes 14 years to quadruple the initial amount money.
Does money double every 8 years? ›
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.
Will my money double in 10 years? ›
The Rule of 72 is focused on compounding interest that compounds annually. For simple interest, you'd simply divide 1 by the interest rate expressed as a decimal. If you had $100 with a 10 percent simple interest rate with no compounding, you'd divide 1 by 0.1, yielding a doubling rate of 10 years.
Why do investments double every 7 years? ›
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.
