Enter two different related values into the calculator to determine the relative percent difference (RPM) between them.

RPD Formula

The following formula is used to calculate a relative percent difference (RPD.)

RPD = [X2-X1] / [[X2+X1]/2] *100

  • Where RPD is the relative percent difference (%)
  • X2 is the final value
  • X1 is the initial value

RPD Definition

What is RPD?

RPD, short for relative percent difference, is a measure of the change in a value relative to the average of that value.

For example, if a value in an experiment changed from 10 to 20, the RPD would be relative to the average of those two numbers. 10 + 20 /2 = 15.

Example Problem

How to calculate RPD?

  1. First, determine the initial value.

    For this example problem, we will look at the price of a TV over time. The initial price of the TV is found to be $500.00.

  2. Next, determine the final value.

    After two years time, the TV price goes up to $750.00.

  3. Finally, calculate the RPD.

    The relative percent difference is then calculated using the formula above:
    RPD = [X2-X1] / [[X2+X1]/2] *100
    RPD = [750-500] / [[750+500]/2] *100
    RPD = 40%