How percentage difference is worked out
Both values carry equal weight. Swapping them leaves the percentage difference unchanged.
Percentage difference = |A − B| ÷ ((A + B) ÷ 2) × 100
- Subtract the two values and take the absolute difference.
- Add the values and divide by 2 to find their average.
- Divide the absolute difference by the average and multiply by 100.
- For the reference changes, divide the signed change by its starting value instead.
Worked example: For 10 and 6, the absolute difference is 4 and the average is 8. Then 4 ÷ 8 × 100 = 50%. From 10 to 6 is a 40% decrease, but from 6 to 10 is a 66.67% increase.
Common percentage differences
| Value A | Value B | Percentage difference | Absolute difference | Average |
|---|---|---|---|---|
| 10 | 6 | 50% | 4 | 8 |
| 50 | 40 | 22.22% | 10 | 45 |
| 100 | 120 | 18.18% | 20 | 110 |
| 3.5 | 4 | 13.33% | 0.5 | 3.75 |
| 200 | 100 | 66.67% | 100 | 150 |
| 1 | 3 | 100% | 2 | 2 |
Swipe the table sideways to see the rest.
Both values use the same units. Neither is treated as the starting point.
Things to consider
- Use difference when neither value comes first.
- Use percentage change for a before-and-after comparison.
- Use the same units for both values.
- Negative values can make this formula harder to interpret.
Frequently asked questions
What is the percentage difference formula?
Take |A − B|, divide by (A + B) ÷ 2, and multiply by 100. For 10 and 6, this is 4 ÷ 8 × 100 = 50%. If both values are 0, there is no difference. If non-zero values average to 0, the percentage difference is undefined.
What is the difference between percentage difference and percentage change?
Difference uses the average of both values. Change uses an original value. Use the Percentage Increase and Change Calculator when one value is the starting point.
Why does the order not matter?
The absolute difference and the average stay the same when you swap A and B. Percentage change does not behave this way because its starting value changes.
When should I use percentage difference?
Use it to compare two measurements or prices with no before-and-after order and no accepted reference value. It is usually used for positive values.
Can percentage difference exceed 100%?
Yes. For non-negative values with a positive average, it can reach 200%. Comparing 1 and 3 gives 100%; comparing 0 and 10 gives 200%. That limit does not apply to mixed positive and negative values.
How is percentage difference different from percentage error?
Percentage error compares a measured value with an accepted reference, using the absolute reference value as the base. Percentage difference gives both values equal weight and uses their average.
Results are estimates for general information only, not financial, medical or professional advice.