What is the Rule of 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.
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.
The Rule of 72 helps investors understand how long it will take for their initial investment to double. Understanding at an early age how money grows is important. Time is a key component to building a respectable savings for later in life.
With an estimated annual return of 7%, you'd divide 72 by 7 to see that your investment will double every 10.29 years.
Currently, money market funds pay between 4.47% and 4.87% in interest. With that, you can earn between $447 to $487 in interest on $10,000 each year. Certificates of deposit (CDs). CDs are offered by financial institutions for set periods of time.
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.
The Rule of 72 is derived from a more complex calculation and is an approximation, and therefore it isn't perfectly accurate. The most accurate results from the Rule of 72 are based at the 8 percent interest rate, and the farther from 8 percent you go in either direction, the less precise the results will be.
The Rule of 69 is used to estimate the amount of time it will take for an investment to double, assuming continuously compounded interest. The calculation is to divide 69 by the rate of return for an investment and then add 0.35 to the result.
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.
Take it from Einstein: "Compound interest is the eighth wonder of the world. He who understands it, earns it. He who doesn't, pays it." The Rule of 72 is a simple shortcut to approximate how long it will take money in an account to double.
Limitations to the Rule of 72
The rule only applies to investments that offer a fixed rate of return. If the investment offers a variable rate of return, the actual period required for doubling could be materially different. The rule only applies only works for periods of time long enough for an amount to double.
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%.
You can also run it backwards: if you want to double your money in six years, just divide 6 into 72 to find that it will require an interest rate of about 12 percent. where Y and r are the years and interest rate, respectively.
The Rule of 72 is a handy tool used in finance to estimate the number of years it would take to double a sum of money through interest payments, given a particular interest rate. The rule can also estimate the annual interest rate required to double a sum of money in a specified number of years.
With a retirement account of $300,000, this means an average return of about $15,000 per year.
Bank Savings Accounts
As noted above, the average rate on savings accounts as of February 3rd 2021, is 0.05% APY. A million-dollar deposit with that APY would generate $500 of interest after one year ($1,000,000 X 0.0005 = $500). If left to compound monthly for 10 years, it would generate $5,011.27.
If you were to place $500,000 in a high-yield savings account with a 2.15% APY and wait one year, you will have earned $10,750 in interest. This rate is likely insufficient to keep up with annual inflation, which means your money will become less valuable at a higher rate than when it's accruing interest.
The rule of 72 is best for annual interest rates. On the other hand, the rule of 70 is better for semi-annual compounding. For example, let's suppose you have an investment that has a 4% interest rate compounded semi-annually or twice a year. According to the rule of 72, you'll get 72 / 4 = 18 years.
The so-called Rule of 42 is one example of a philosophy that focuses on a large distribution of holdings, calling for a portfolio to include at least 42 choices while owning only a small amount of most of those choices.
According to conventional wisdom, an annual ROI of approximately 7% or greater is considered a good ROI for an investment in stocks. This is also about the average annual return of the S&P 500, accounting for inflation. Because this is an average, some years your return may be higher; some years they may be lower.
If you expect your wealth to grow by 12% a year, then it would take 6 years (72/12 = 6) to double.
Some experts say to have at least eight to 10 times your salary available to you once you enter retirement. Others say you need at least 65% to 80% of your pre-retirement income available to you each year. There are also general savings recommendations by age, and, finally, there's the 4% rule, too.