**Rule of 70** is a formula for calculating how long it will take for your money to double at a given rate of return.

The rule is frequently applied to compare investments with different annual compound interest rates in order to quickly determine how long an investment will grow. The **rule of 70** is also known as the **doubling time rule**.

## What Is the 70-Year Rule & Formula

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## Calculate the investment or variable’s annual rate of return or growth rate. Subtract 70 from the annual growth rate or yield.

The rule of 70 can assist investors in determining the future value of an investment.

The rule is very effective in determining how many years it will take for an investment to double, despite the fact that it is a rough estimate.

This metric can be used to assess a variety of investments, such as mutual fund returns and the growth rate of a retirement portfolio.

If the calculation yielded a result of 15 years for a portfolio to double, for example, an investor who wants the result to be closer to 10 years could make changes to the portfolio’s allocation to try to increase the growth rate.

The rule of 70 is widely accepted as a method for dealing with exponential growth concepts without resorting to complicated mathematical procedures.

When examining the potential growth rate of an investment, it is most commonly associated with items in the financial sector.

An estimate in years can be obtained by dividing the number 70 by the predicted rate of growth, or return on financial transactions.

### The 72nd and 69th Rules

The rule of 72 or the rule of 69 are used in some cases. The function is similar to the rule of 70, but instead of 70, the calculations use the numbers 72 or 69, respectively.

While the rule of 69 is often thought to be more accurate when dealing with continuous compounding processes, the rule of 72 may be more accurate for compounding intervals that are less frequent. The rule of 70 is frequently used because it is simple to remember.

### Other Uses of the 70th Percentile Rule

The rule of 70 can also be used to estimate how long it will take a country’s real gross domestic product (GDP) to double.

We could use the GDP growth rate in the rule’s divisor, similar to how we calculate compound interest rates.

For example, if China’s growth rate is 10%, the rule of 70 predicts that China’s real GDP will double in seven years, or 70/10.

### Real Growth vs. the Rule of 70

It’s vital to keep in mind that the rule of 70 is a guess based on projected growth rates. If growth rates fluctuate, the original calculation may turn out to be incorrect.

In 1953, the population of the United States was predicted to be 161 million people; by 2015, it had nearly doubled to 321 million people.

The growth rate was recorded as 1.66 percent in 1953. By 1995, the population would have doubled according to the rule of 70.

Changes in the growth rate, on the other hand, dropped the average rate, rendering the rule of 70 calculation erroneous.

The rule of 70 formula provides direction for dealing with difficulties of compounding interest and exponential growth, albeit it is not a perfect estimate.

This principle can be applied to any instrument that is expected to grow steadily over time, such as population growth.

The rule, on the other hand, does not work effectively when the growth rate is expected to change substantially.

The rule of 70 is a formula for calculating how long it will take your money or an investment to double at a certain rate of return.

This statistic can be used to assess a variety of assets, such as mutual fund returns and the growth rate of a retirement portfolio.

It’s vital to keep in mind that the rule of 70 is a guess based on projected growth rates. If growth rates alter, the original calculation may turn out to be incorrect.

### Using the Rule of 70 as an example

Consider the following scenario: an investor is analysing their retirement account and wants to know how many years it will take to double the fund at various rates of return.

Several estimations of the rule of 70 based on various growth rates are outlined below.

### Compound Interest and the Rule of 70: What’s the Difference?

Compound interest (also known as compounding interest) is interest computed on the initial principal of a deposit or loan, as well as all of the accrued interest from previous periods.

Compound interest accrues at a rate determined by the frequency of compounding, with the higher the number of compounding periods, the higher the compound interest rate.

Compound interest is a key component in determining investment long-term growth rates and the various doubling rules.

If interest earned is not reinvested, the number of years it takes for the investment to double will be longer than if interest is reinvested.

### The Rule of 70’s Limitations

As previously stated, predictions of growth rates or investment rates of return are included in the rule of 70 and any of the doubling rules.

As a result, because the rule of 70 is limited in its ability to foresee future growth, it can produce erroneous conclusions.

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