# Calculating Percent Difference

Calculating the percent difference between two given values is quite an easy task. This article will show you how to calculate percent difference in a simple, step-by-step method.

Amruta Deshpande

Last Updated: Mar 26, 2018

We'll have a look at how the percent difference formula works, along with a couple of examples that show how simple this calculation really is.

Percent Difference Formula

Percent difference is calculated as the difference between two values, divided by the average of the two values, expressed in terms of percentage.

While calculating the percent difference, always use absolute values, i.e. ignore the minus sign before any of the values. For example, a subtraction of 5 minus 10 gives -5. But the absolute value would be taken as 5, without any minus sign.

**Percent Difference = [First Value - Second Value] ÷ [(First Value + Second Value) ÷ 2] × 100****Using Absolute Values**While calculating the percent difference, always use absolute values, i.e. ignore the minus sign before any of the values. For example, a subtraction of 5 minus 10 gives -5. But the absolute value would be taken as 5, without any minus sign.

When to Use and When Not to Use Percent Difference Formula?

Some people may get confused about using the percent difference formula, and other related formulae for calculating percentage change or percentage error.

Use percentage change formula when you have one old and one new value, and you want to know the relative change in percentage, with reference to the old value.

If you have one exact or theoretical value, and one approximate or observed value, use the percent error formula.

Use percentage change formula when you have one old and one new value, and you want to know the relative change in percentage, with reference to the old value.

**Example:**Percent increase in the price of a product, or percent increase in the population of a country over the last year.**Percent Change = New Value - Old Value ÷ Old Value × 100**If you have one exact or theoretical value, and one approximate or observed value, use the percent error formula.

**Example:**Percent error in the actual and observed values in a scientific experiment.**Percent Error = Approximate Value - Exact Value ÷ Exact Value × 100**How to Find Percent Difference

Example 1

**Sam weighs 160 pounds, while Ron weighs 120 pounds. What is the percent difference between the weights of Sam and Ron?**

**Find the percent difference**

Percent Difference = [First Value - Second Value] ÷ [(First Value + Second Value) ÷ 2] × 100

= [160 - 120] ÷ [(160 + 120) ÷ 2] × 100

Percent Difference = 40 ÷ 140 × 100

**Percent Difference = 28.57%**

Example 2

Here is a problem for you to try out. To view the solution, click on the 'show answer' link provided below.

» What is the percent difference between the population of city A, with a population of 2.5 million, and city B, with a population of 1.2 million?

» What is the percent difference between the population of city A, with a population of 2.5 million, and city B, with a population of 1.2 million?