Rule of 70 Calculator

What is the Rule of 70?

The Rule of 70 is a simple method used to estimate the number of years it will take for an investment to double in value, given a fixed annual rate of return. It's a quick and easy way to gauge the potential growth of an investment over time.

The Rule of 70 Formula

The formula for the Rule of 70 is:

\[T \approx \frac{70}{r}\]

Where:

• \(T\) = Time to double the investment (in years)
• \(r\) = Annual interest rate (as a percentage)

Step-by-Step Rule of 70 Calculation

1. Identify the annual interest rate (r) for your investment.
2. Divide 70 by this interest rate.
3. The result is the approximate number of years it will take for your investment to double.

Example Calculation

Let's calculate the doubling time for an investment with an annual interest rate of 7%:

1. \(r = 7\%\)
2. \(T \approx \frac{70}{7} = 10\) years

Therefore, at a 7% annual interest rate, an investment would take approximately 10 years to double in value.

Visual Representation

The green portion represents the initial investment, which doubles over the calculated time period to fill the entire bar.