Percent Difference Calculator
Find the percentage difference between two numbers, using the average as the reference, with the absolute difference shown too
Last updated: November 2, 2026
How to Use the Percent Difference Calculator
How to calculate the percent difference
- Enter the first value.
- Enter the second value. The order does not matter.
- Read the percent difference. The result also shows the absolute difference, the average of the two values, and, for comparison, the percent change from the first value to the second.
The values can be any size and can include decimals. If both values are zero, the percent difference is undefined.
Formula & Methodology
Percent difference formula
Percent difference = |A − B| ÷ ((|A| + |B|) ÷ 2) × 100
The difference between the two values is divided by their average, so neither number is treated as the "original". Swap A and B and you get the same answer.
Worked example
Compare 50 and 80.
- Absolute difference = |50 − 80| = 30
- Average = (50 + 80) ÷ 2 = 65
- Percent difference = 30 ÷ 65 × 100 = 46.15%
Percent difference vs percent change
They answer different questions and give different numbers:
| | Percent difference | Percent change | |---|---|---| | Reference | Average of both values | The first (original) value | | Formula | |A − B| ÷ average × 100 | (B − A) ÷ |A| × 100 | | Order matters? | No | Yes | | 50 and 80 | 46.15% | 60% (an increase) | | 80 and 50 | 46.15% | −37.5% (a decrease) |
Use percent difference when you are comparing two values on equal footing, such as two measurements, two prices from different shops, or two groups. Use percent change when one value is the starting point, such as a price before and after a rise.
About Percent Difference Calculator
Our percent difference calculator is a free, easy-to-use tool designed to help youfind the percentage difference between two numbers, using the average as the reference, with the absolute difference shown too. If you're a professional or just need quick calculations, our calculator provides accurate results instantly.
Frequently Asked Questions
How do you calculate percent difference?
Subtract the two numbers, take the absolute value, divide by the average of the two numbers, and multiply by 100. For 50 and 80 that is 30 ÷ 65 × 100 = 46.15%.
What is the difference between percent difference and percent change?
Percent change measures how much a value moved from a starting point, so the order matters (50 to 80 is +60%, 80 to 50 is −37.5%). Percent difference compares two values symmetrically using their average, so the order does not matter and 50 vs 80 is 46.15% either way.
When should I use percent difference?
When neither value is the "original": comparing two experimental measurements, the prices of the same item at two stores, or the results of two groups. It is common in science and lab reports.
Why is percent difference not the same as the percentage increase?
Because they use different denominators. Percentage increase divides by the original value, while percent difference divides by the average of both. Use the percentage increase calculator when you have a clear before and after.
Can the percent difference be more than 100%?
Yes. For example, 10 and 100 have a difference of 90 and an average of 55, which gives 163.6%. The maximum for two positive numbers approaches 200%, when one value is tiny compared with the other.
What if one of the numbers is zero?
It still works as long as the other number is not zero. Comparing 0 with 10 gives a difference of 10 and an average of 5, so the percent difference is 200%. If both are zero the result is undefined.
Does it work with negative numbers?
Yes. The formula uses the absolute values of the numbers in the denominator, so the result is always a positive percentage. For negative values, consider whether percent difference is the right measure for your data.
Your result will appear here
Loading…