What is percentage difference?
Percentage difference shows how far apart two numbers are relative to their size, without choosing either one as the starting point. It is useful for comparing two prices, two measurements or two scores that exist side by side rather than one after the other.
Percentage difference formula
percentage difference = |a − b| ÷ ((|a| + |b|) ÷ 2) × 100
The vertical bars mean the absolute value, so the result is never negative and does not depend on the order of the numbers.
Step-by-step example
Compare 80 and 60.
| Step | Calculation | Result |
|---|---|---|
| 1. Find the difference | 80 − 60 | 20 |
| 2. Find the average | (80 + 60) ÷ 2 | 70 |
| 3. Divide | 20 ÷ 70 | 0.2857 |
| 4. Convert to percent | 0.2857 × 100 | 28.57% |
Percentage difference vs percentage change
The same two numbers give different answers when one of them is the starting value. Going from 80 down to 60 is a 25% decrease, and going from 60 up to 80 is a 33.33% increase. The percentage difference is 28.57% either way. Use the percentage increase calculator or the percentage decrease calculator when one value is the original.
Common mistakes
- Dividing by one of the values instead of the average.
- Using it when one value is clearly the original. That is a percentage change.
- Forgetting that the order of the two values does not matter.
How to use this calculator
- Enter your values. Compare two values as a percentage when neither one is the starting point.
- Check units and assumptions. Make sure the inputs use the same scale and that any optional settings match your situation.
- Calculate and review. Compare the output with the formula below and note any limitations stated on the page.
Formula and calculation method
Use the relevant percentage relationship shown on this page. For a change between two values, compare the difference with the correct reference value; for reverse calculations, rearrange the equation to solve for the missing starting value.
Worked example
For example, if a price changes from $60 to $80, the difference is $20. Dividing $20 by the starting value of $60 and multiplying by 100 gives a 33.33% increase. Always use the original value as the denominator for percentage increase.
Search and practical tips
People commonly search for a percentage difference calculator – free tool, how to calculate the result step by step, which formula to use, and how to check the answer manually. Use the formula above as a transparent starting point, and consult the relevant institution, agency, or qualified professional when an official rule or personal circumstances affect the result.
Frequently asked questions
What is the percentage difference formula?
Percentage difference = |a − b| ÷ ((|a| + |b|) ÷ 2) × 100. You divide the gap between the two values by their average and convert to a percent.
What is the difference between percentage difference and percentage change?
Percentage change treats one value as the starting point and divides by it. Percentage difference treats both values equally and divides by their average, so the answer is the same whichever value you enter first.
Can percentage difference be more than 100%?
Yes. If one value is much larger than the other the result can exceed 100%. For example, 10 and 200 differ by about 180.95%.
What happens if one of the values is zero?
The result is 200%, because the difference equals the average multiplied by two. If both values are zero there is no difference and the result is 0%.
When should I use percentage difference?
Use it to compare two independent measurements, such as the prices of two products or the results of two experiments, when neither is the reference value.