This simple formula tells you how long it will take for your money to double—while you sit back and relax (2024)

If you put your money in the right places, it can grow substantially over time, thanks to the power of compound interest. It could even double, while you don't have to do a thing.

Want to figure out just how fast your money could grow? The "Rule of 72" approximates how many years it will take for your money to double, given a fixed rate of return.

"Think about your savings for the future," Tom Mathews and Steve Siebold write in their book "How Money Works," which highlights the "Rule of 72" as of one of three essential personal finance topics to understand (the other two being compound interest and the time value of money). "The Rule of 72 can give you an idea of how many doubles you'll get in your lifetime. With more time, a lower interest rate may give you enough to nail your goals. With less time, you may need a higher interest rate."

The formula is simple: 72 / interest rate = years to double

Try plugging in various interest rates from the different accounts your money is in, from savings and money market accounts to index and mutual funds. For example, if your account earns:

1%, it will take 72 years for your money to double (72 / 1 = 72)
3%, it will take 24 years for your money to double (72 / 3 = 24)
6%, it will take 12 years for your money to double (72 / 6 = 12)
9%, it will take 8 years for your money to double (72 / 9 = 8)
12%, it will take 6 years for your money to double (72 / 12 = 6)

If your money sits in a standard savings account and earns just 0.09% (the average interest rate for savings accounts nationwide), it would take 800 years to double.

If you have extra savings, you're probably better off keeping it in a high-yield savings account or certificate of deposit, which both offer significantly higher interest rates, up to 2.69%.

If you invest your money in the stock market, whether through an employer-sponsored 401(k) plan, a traditional or Roth IRA, an individual brokerage account or somewhere else, you'll likely see even bigger returns. The average annualized total return for the S&P 500 index over the past 90 years is 9.8%. Adjusted for inflation, it still comes to an annual return of around 7% to 8%. If you earn 7%, your money will double in a little over 10 years.

This simple formula tells you how long it will take for your money to double—while you sit back and relax (1)

VIDEO2:1502:15

How compound interest works

You can also use the Rule of 72 to plug in interest rates from credit card debt, a car loan, home mortgage, or student loan to figure out how many years it'll take your money to double for someone else.

For example, the average interest rate for credit cards is 17.3%. If you divide 72 by that rate, you get 4.16 years. That's all it takes for a credit card company to earn double your money. The higher the interest rate, the more you'll owe to your lenders.

If you have debt, look into the possibility of refinancing your car loan or mortgage to get a lower interest rate.

The "Rule of 72" is "a practical eye opener that forces you to ask shrewd questions before making important money decisions," Mathews and Siebold write. If you understand and apply it to your personal finances, "you're less likely to fall for gimmicky promotions from banks, settle for opportunities that don't give you the advantage, and take on debt that might take forever to pay off."

Don't miss: Most Americans don't understand a money term that can help you save hundreds of thousands of dollars

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This simple formula tells you how long it will take for your money to double—while you sit back and relax (2)

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David Bach: This simple chart changed the way I think about money

This simple formula tells you how long it will take for your money to double—while you sit back and relax (2024)

FAQs

This simple formula tells you how long it will take for your money to double—while you sit back and relax? ›

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.

What is the formula for calculating how long it will take your money to double? ›

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.

What is the formula to determine how long it will take for your money to double at any given interest rate known as? ›

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 a formula that helps you know when your money will double in value? ›

How Do You Calculate 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.

What is a simple way to figure out how to double your money in a savings account or an investment? ›

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. For example, if you earn an 8 percent annual return, it will take about 9 years to double.

What is the formula for simple interest? ›

How to Calculate Simple Interest? Simple Interest is calculated using the following formula: SI = P × R × T, where P = Principal, R = Rate of Interest, and T = Time period.

How do you double a amount of money? ›

The Classic Way

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.

How quickly should you double your money? ›

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).

Does the Rule of 72 tells you how long it will take to double your money? ›

What Is the Rule of 72? The rule of 72 is a shortcut investors can use to determine how long it will take their investment to double based on a fixed annual rate of return. 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.

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.

What is the formula for calculating the value of money? ›

The Future Value (FV) formula in TVM is FV = PV * (1 + r)^n, where PV represents present value or the current worth of a future amount, r is the interest rate (annually growth rate), and n is the number of periods (e.g., years) the money is invested or borrowed for.

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.

Why is 72 the Rule of 72? ›

The value 72 is a convenient choice of numerator, since it has many small divisors: 1, 2, 3, 4, 6, 8, 9, and 12. It provides a good approximation for annual compounding, and for compounding at typical rates (from 6% to 10%); the approximations are less accurate at higher interest rates.

How long does it take to double your 401k? ›

Your investments

With an annual 4% return, it would take 18 years (72/4) to approximately double. With a 6% return, it would take 12 years (72/6), while with an 8% return it would take 9 years (72/8).

How long does it take to double your money at 7 percent? ›

If you earn 7%, your money will double in a little over 10 years. You can also use the Rule of 72 to plug in interest rates from credit card debt, a car loan, home mortgage, or student loan to figure out how many years it'll take your money to double for someone else.

How long does it take to double your money at 5 percent? ›

It would take 14.4 years to double your money. Applying the rule of 72, the number of years to double your money is 72 divided by the annual interest rate in percentage. In this question, the annual percentage rate is 5%, thus the number of years to double your money is: 72 / 5 = 14.4.

How long does it take to double your money at 8.25 interest? ›

Hence it takes 8.74 years to double the money.

What is the 8 4 3 compounding rule? ›

What is the 8-4-3 rule of compounding? In the 8-4-3 strategy, the average return of a particular investment amount for 8 years is 12 per cent/annum, while after that time period, it will take only half of that horizon, i.e., 4 years (total 12 years), to get a return of 12 per cent.

How long does it take to double your money with 5% interest? ›

Why it Pays to Know the Math
Rate of ReturnRule of 72 # of Years to Double MoneyLogarithmic Formula # of Years to Double Money
4%18.017.7
5%14.414.2
6%12.011.9
7%10.310.2
15 more rows
Sep 14, 2023

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