Rule of 69 Calculator

What is the Rule of 69?

The Rule of 69 is a quick estimation method used in finance to determine how long it will take for an investment to double in value, given a fixed annual rate of return. It's a variation of the more commonly known Rule of 72, but it's considered more accurate for interest rates between 5% and 10%.

The Rule of 69 Formula

The formula for the Rule of 69 is:

\[T = \frac{69}{r}\]

Where:

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

Step-by-Step Rule of 69 Calculation

1. Identify the annual interest rate (r) for your investment.
2. Divide 69 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 8%:

1. \(r = 8\%\)
2. \(T = \frac{69}{8} = 8.625\) years

Therefore, it will take approximately 8.625 years for an investment to double at an 8% annual interest rate.

Visual Representation

The green portion represents the initial investment value, and the blue portion represents the growth to double the initial value over the calculated time period.