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Rule of 70


The Rule of 70 is a financial term used to estimate the number of years it would take for an investment or money in an interest-bearing account to double. It is calculated by dividing the number 70 by the annual rate of return or interest rate. Note that this rule offers an approximation and assumes a constant annual rate.


The phonetics of the keyword “Rule of 70” is /ru:l ʌv ˈsɛvənti/.

Key Takeaways

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  1. The Rule of 70 is a simple mathematical formula used to estimate the time it would take for something to double, given a certain level of continuous steady growth rate. It’s most often used in economics and finance for understanding compound interest or population growth.
  2. The formula for the Rule of 70 is: Time to Double = 70 divided by the Growth Rate. Therefore, if we have a growth rate of 2%, we could estimate that it would take approximately 35 years for the initial amount to double (70 / 2 = 35).
  3. While it’s a helpful tool for quick calculations, it’s important to note that the Rule of 70 is an approximation. Actual results may vary slightly due to a variety of factors, including the variability in the growth rate and initial values.



The Rule of 70 is a significant concept in business and finance since it offers a prompt and straightforward way to estimate the time it takes for an investment or money in an account to double, given a particular annual interest rate. This rule is instrumental in financial planning, helping individuals and businesses understand the power of compound interest and equips them to plan their investments strategically. Furthermore, it assists in comparing different investment options based on their respective rates of interest. The Rule of 70, therefore, contributes to more informed and sound financial decisions.


The Rule of 70 is a financial concept that plays a pivotal role in the understanding and estimation of investment growth over time, along with the measurement of the effect of compounding interest. The purpose of this rule is to provide investors and analysts with a simple and intuitive way of calculating the amount of time it will take for an investment or a certain sum of money to double, given a specific annual rate of increase or interest. Utilizing this calculation tool, one can make quick, but fairly accurate, judgments about the future value of an investment or the potential returns of a venture under certain conditions.The Rule of 70 works by dividing the number 70 by the annual growth rate (in percentage form). For example, if a certain sum of money was invested in a venture that promises a steady annual growth rate of 7 percent, according to the Rule of 70, it would take 10 years (70 divided by 7) for that sum to double. This rule is used frequently in finance and business due to its simplicity and accuracy, providing an easily graspable future financial projection. It assists in making informed decisions about investments, opportunity costs, and the benefits of long-term growth strategies.


The Rule of 70 is a financial term used to calculate the approximate time it would take for an investment or your money to double, given a specified annual rate of return. Here are three real-world examples:1. Retirement Savings: Suppose you have a retirement account with an average annual interest rate of 7%. Using the Rule of 70, you can determine that your investment would double in value about every 10 years (70 divided by 7 equals 10). Therefore, if you have 30 years until you retire, you can expect your investment to double about 3 times (assuming the rate remains consistent).2. Inflation: The Rule of 70 can also be applied to estimate how long it will take for the purchasing power of your money to be halved due to inflation. If the inflation rate is 2% per year, it would take approximately 35 years (70 divided by 2) for the value of your money to drop to half its present value.3. GDP Growth: Governments and finance professionals often use the Rule of 70 to predict the doubling time of a nation’s GDP. If a country’s GDP grows at a rate of 3.5% annually, it would take approximately 20 years (70 divided by 3.5) for the GDP to double.

Frequently Asked Questions(FAQ)

What does the Rule of 70 in finance and business imply?

The Rule of 70 is a calculation to determine how long it would take for an investment or money in a particular interest-earning account to double. It is a simplified way to estimate the effect of exponential growth.

How is the Rule of 70 calculated?

The Rule of 70 calculation is done by dividing 70 by the growth rate or interest rate. For example, if you have an account with an annual compounded interest rate of 4%, it would take approximately 17.5 years for your initial investment to double (70 divided by 4 equals 17.5).

Does the Rule of 70 only apply to finances?

No, the Rule of 70 can also apply to other aspects such as population growth, inflation rates, and resource consumption where exponential growth or decay is involved.

Can the Rule of 70 be used with any Interest rate?

Yes, you can use the Rule of 70 with any interest rate. Please note that it’s a rough estimation, and the results are most accurate with smaller percentages.

Is the Rule of 70 accurate?

While the Rule of 70 provides an easy and quick estimate, it is not always 100% accurate, especially with large growth rates. But it’s sufficiently accurate for practical purposes.

What are some limitations of the Rule of 70?

The Rule of 70 assumes a fixed annual growth rate, which might not always be the case in real-world situations. Also, it is just a mathematical approximation, which might not always give the exact results.

Can I use the Rule of 70 for decreases in value too?

Yes, the Rule of 70 can also be used for decreases in value, like depreciation or decline in a population, by using a negative growth rate.

What is the importance of the Rule of 70 in finance and business?

The Rule of 70 gives investors and business owners a simple method to estimate the time required for an investment to double. This allows for quick comparison of the potential profitability of various opportunities without complex calculations.

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