The Rule of 72 | Primerica (2024)

FAQs

What is the Rule of 72 answer? ›

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.

So, if the interest rate is 6%, you would divide 72 by 6 to get 12. This means that the investment will take about 12 years to double with a 6% fixed annual interest rate.

If you need to double your financial investment in 10 years, a savings account with a 5% interest rate, for instance, wouldn't help achieve your goals. You'd need something with a higher rate of return (at least 7.2%) to make that 10-year milestone happen.

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.

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%. The Rule of 72 can be applied to anything that increases exponentially, such as GDP or inflation; it can also indicate the long-term effect of annual fees on an investment's growth.

Summary: An investment of $10000 today invested at 6% for five years at simple interest will be $13,000.

t = ln(100,000/5,000)/0.097 ≈ 12.35 years Using the formula for continuous compounding interest, it will take approximately 12.35 years for a $5,000 investment to grow to $100,000 at an interest rate of 9.7% compounded continuously.

Final answer:

It will take approximately 15.27 years to increase the $2,200 investment to $10,000 at an annual interest rate of 6.5%.

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.

How can I double my money legally fast? ›

The classic approach of doubling your money involves investing in a diversified portfolio of stocks and bonds and is probably the one that applies to most investors.

Rule 72(t) allows for penalty-free withdrawals from Individual Retirement Accounts (IRAs) and other tax-advantaged retirement accounts like 401(k) and 403(b) plans. It is issued by the Internal Revenue Service (IRS).

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.

Yes, the Rule of 72 can apply to debt, and it can be used to calculate an estimate of how long it would take a debt balance to double if it's not paid down or off.

Lower or higher rates outside of this range can be better predicted using an adjusted Rule of 71, 73 or 74, depending on how far they fall below or above the range. You generally add one to 72 for every three percentage point increase. So, a 15% rate of return would mean you use the Rule of 73.

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.

One can also use this to compute the returns a portfolio should generate to double money in a given time period. If you want to double it in five years, the portfolio should be invested such that it yields 72/5=14.4%.