Rule of 70 Vs. Rule of 72: Definition, How They Work, and Example (2024)

FAQs

Rule of 70 Vs. Rule of 72: Definition, How They Work, and Example? ›

The Rule of 70 is a calculation that determines how many years it takes for an investment to double in value based on a constant rate of return. The Rule of 72 is a shortcut or rule of thumb used to estimate the number of years required to double your money at a given annual rate of return and vice versa.

Hence, the doubling time is simply 70 divided by the constant annual growth rate. For instance, consider a quantity that grows consistently at 5% annually. According to the Rule of 70, it will take 14 years (70/5) for the quantity 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.

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 reason why the rule of 70 is popular in finance is because it offers a simple way to manage complicated exponential growth. It breaks down growth formulas into a simple equation using the number 70 alongside the rate of return.

‍To give a better sense of what this means in practicality, we thought it would help to run through an example: A properties ARV is $200,000 and it needs an estimated $30,000 in repairs. The 70% rule states on this occasion, that an investor should pay $110,000. ($200,000 x 70%) – $30,000 = $110,000.

The Rule of 70

For example, assume an investor invests $10,000 at a 10% fixed annual interest rate. He wants to estimate the number of years it would take for his investment to grow to $20,000. He uses the rule of 70 and determines it would take approximately seven (70/10) years for his investment 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.

What Is the Rule of 72? 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.

When buying a home to flip, investors need to estimate how much they believe the property could sell for after it's been renovated. They can then multiply that amount by 70% and subtract it from the estimated cost of renovating the property.

What are the flaws of Rule of 72? ›

There are a few key drawbacks to using the Rule of 72, including the fact that it's mostly accurate only for a certain subset of investments, it's only an estimation, and that unforeseen factors can cause the rate of return for an investment to change, rendering it useless.

The rule of 70 gives you an estimate of the number of years it will take some quantity to double given the annual percentage growth rate. Someone sat down and did the math and it turned out that the number of years to double is about 70 / the annual growth rate in percent.

The rule of 70 is an easy method of estimating how quickly a variable will double if you know its annual growth rate. If a variable is growing at a rate of x% per period, you simply take 70 and divide it by x. The rule of 70 is useful for all sorts of applications.

Basically, the rule says real estate investors should pay no more than 70% of a property's after-repair value (ARV) minus the cost of the repairs necessary to renovate the home. The ARV of a property is the amount a home could sell for after flippers renovate it.

For example, if the growth rate for China is estimated as 10%, the Rule of 70 predicts it would take seven years, or 70/10, for China's real GDP to double.

The 70% rule for retirement savings can help you estimate the amount of income you may need in retirement. It says you'll need 70% of your pre-retirement, post-tax income to retire comfortably.