Percentage Difference Calculator

Use this percentage difference calculator to compare two values and find how far apart they are as a percentage of their average value.

Enter Value 1 and Value 2 to calculate the percentage difference, absolute difference, average, and calculation steps.

What Is Percentage Difference?

Percentage difference measures how different two values are from each other when neither value is considered the original or starting value.

This is the key idea behind percentage difference.

Suppose you have two values:

• Value 1 = 80
• Value 2 = 100

You are simply comparing 80 and 100. You are not saying that 80 was the original value and 100 is the new value.

Because neither value is the starting point, the calculation uses the average of the two values as the reference.

The formula is:

Percentage Difference = (Absolute Difference ÷ Average of the Two Values) × 100

For 80 and 100:

• Absolute difference = |80 − 100| = 20
• Average = (80 + 100) ÷ 2 = 90
• Percentage difference = (20 ÷ 90) × 100
• Percentage difference = 22.22%

So, 80 and 100 have a percentage difference of 22.22%.

Percentage Difference Formula

The percentage of difference formula is:

Percentage Difference = |Value 1 − Value 2| ÷ ((Value 1 + Value 2) ÷ 2) × 100

In simpler steps:

1. Find the difference between the two values.

2. Find the average of the two values.

3. Divide the difference by the average.

4. Multiply by 100.

The absolute value | | ensures that the difference is positive. Therefore, changing the order of the two values does not change the percentage difference.

How to Calculate Percentage Difference

To calculate the percentage difference, use these three main steps.

Step 1: Find the Absolute Difference

Subtract one value from the other and ignore the negative sign.

Absolute Difference = |Value 1 − Value 2|

Example:

|80 − 100| = 20

Step 2: Find the Average

Add the two values and divide by 2.

Average = (Value 1 + Value 2) ÷ 2

Average = (80 + 100) ÷ 2 = 90

Step 3: Calculate the Percentage Difference

Divide the absolute difference by the average and multiply by 100.

Percentage Difference = (20 ÷ 90) × 100

= 22.22%

Therefore, the percentage difference between 80 and 100 is 22.22%.

Percentage Difference Between Two Numbers

When someone asks for the percentage difference between two numbers, they usually want to know how far apart the two numbers are relative to their average.

For example, consider 50 and 70.

Difference:

|50 − 70| = 20

Average:

(50 + 70) ÷ 2 = 60

Percentage Difference:

(20 ÷ 60) × 100 = 33.33%

Therefore, the percentage difference between 50 and 70 is 33.33%.

The order does not matter:

50 and 70 → 33.33%

70 and 50 → 33.33%

This is because percentage difference is a comparison rather than a directional change.

Why Does Percentage Difference Use the Average?

When neither value is the starting point, there is no single original value to use as the reference.

For example, with 80 and 100, choosing 80 as the reference would produce one result, while choosing 100 would produce another.

Using their average gives both values equal importance:

Average = (80 + 100) ÷ 2 = 90

The difference of 20 is therefore compared with 90:

20 ÷ 90 × 100 = 22.22%

This is why the average of the two values is used in the standard percentage difference formula.

Percentage Difference Examples

Percentage Difference for Rates

The Percentage difference can also be used to compare two rates when neither rate is being treated as the original.

For example, suppose two measurements are:

• Rate 1 = 40
• Rate 2 = 50

Difference:

|40 − 50| = 10

Average:

(40 + 50) ÷ 2 = 45

Percentage difference:

(10 ÷ 45) × 100 = 22.22%

So, the two rates have a 22.22% percentage difference.

Absolute Difference vs Percentage Difference

These two measurements are related but not the same.

Absolute difference tells you the numerical distance between two values.

Percentage difference expresses that distance as a percentage of their average.

For example, for 80 and 100:

Absolute difference = 20

Percentage difference = 22.22%

The absolute difference is useful when you care about the actual number of units. Percentage difference is useful when you want to understand the relative size of the difference.

Does the Order of Values Matter?

No.

Percentage difference uses the absolute difference, so the order of the values does not affect the result.

For example:

80 and 100

and

100 and 80

both produce:

22.22%

This is another important distinction from percentage change, where the original and new values have specific roles.

Common Uses of Percentage Difference

Percentage difference can be useful when comparing:

• Two measurements
• Two rates
• Two test results
• Two quantities
• Two prices when neither is treated as the original
• Two estimates
• Two experimental results
• Two calculated values
• Two values from different sources

The same formula can be used as long as you are comparing the two values rather than measuring a change from one to the other.

Frequently Asked Questions