Enter the annual growth rate into the calculator to determine the doubling time.

Rule Of 70 Doubling Time Formula

The following formula is used to calculate the doubling time using the Rule of 70.

T = 70 / r


  • T is the doubling time (years)
  • r is the annual growth rate (percentage)

To calculate the doubling time, divide 70 by the annual growth rate. The result will be the number of years it takes for the initial amount to double.

What is a Rule Of 70 Doubling Time?

The Rule of 70 Doubling Time is a mathematical formula used in finance and economics to estimate the amount of time it would take for an investment or money in an account to double, given a specified rate of return or interest. The rule states that you can approximate the doubling time by dividing 70 by the rate of return (expressed as a percentage). For example, if the rate of return is 7%, the doubling time would be approximately 10 years (70 divided by 7).

How to Calculate Rule Of 70 Doubling Time?

The following steps outline how to calculate the Rule Of 70 Doubling Time.

  1. First, determine the annual growth rate (r) as a percentage.
  2. Next, use the formula T = 70 / r to calculate the doubling time (T) in years.
  3. Finally, calculate the Rule Of 70 Doubling Time.
  4. After inserting the variables and calculating the result, check your answer with the calculator above.

Example Problem : 

Use the following variables as an example problem to test your knowledge.

annual growth rate (r) = 5%