Math
Percentage Difference Calculator
Percent difference measures how far apart two values are relative to their average, so it does not matter which one you type first.
Enter two numbers to get the percent difference with steps, plus the percent change in each direction so you can see why the two measures disagree and choose the right one.
Either value; order does not change the percent difference.
The other value.
Try an example
Result
Percent difference
—
- Absolute difference
- —
- Average of the two
- —
- Percent change (first → second)
- —
- Percent change (second → first)
- —
Student quick launch
Grade planning, algebra checks, and formulas students reach for most.
Study path
Use this calculator with
Follow these when you want the formula behind the answer, a short lesson, or nearby tools in the same topic.
Percent difference formula
Percent difference divides the gap between two values by their average instead of by one of them. Because the average treats both values equally, the answer is the same no matter which value comes first. Use it when neither value is the 'original' or 'correct' one, such as comparing two measurements, two prices, or two survey results.
Percent difference vs percent change vs percent error
| Measure | Base | Use when | 50 and 70 |
|---|---|---|---|
| Percent difference | average of both | neither value is the reference | 33.33% |
| Percent change | the starting value | one value came before the other | +40% (50 → 70) or -28.57% (70 → 50) |
| Percent error | the accepted value | one value is known to be correct | 28.57% if 70 is accepted |
For 50 and 70 the gap is 20 and the average is 60, so the percent difference is 33.33%. Percent change from 50 to 70 is 40% (base 50) while from 70 to 50 it is 28.57% (base 70). Percent difference sits between the two and is the honest choice when you have no reason to favor either base.
How to use it
- Type the two values in either order.
- Read the percent difference and the absolute difference and average used to compute it.
- Compare it with the two percent-change lines to decide which measure your situation needs.
- Open Show the work to see each step with your numbers.
How to read the answer
The percent difference tells how large the gap is compared with a typical (average) value of the pair. 0% means the values are equal. The percent-change lines show what you would get by treating one value as the starting point; if one value really is the starting point, report that percent change instead.
Common mistakes and edge cases
- Percent difference and percent change are different measures. Do not report one when the other is expected.
- Dividing by one of the values instead of the average gives a percent change, which depends on the order.
- When both values are 0 there is nothing to compare and the result is undefined.
- Negative values are handled with How far a number sits from zero, so the answer is never negative. in the average, but comparing values on opposite sides of zero rarely makes sense as a percent.
- A percent difference above 100% is a sign to use a ratio instead.
Worked examples
Typical
50 and 70
Percent difference
33.3333%
Order does not matter
70 and 50
Percent difference
33.3333%
Equal values
25 and 25
Percent difference
0%
Far apart
10 and 50
Percent difference
133.3333%
Decimals
2.5 and 3.1
Percent difference
21.4286%
One value zero
0 and 8
Percent difference
200%
Negative value
-20 and 30
Percent difference
200%
Both zero
0 and 0 is undefined
Percent difference
Error
Frequently asked questions
What is the difference between percent difference and percent change?+
Percent change divides by the starting value and depends on direction. Percent difference divides by the average of the two values and is the same in both directions.
How do you calculate percent difference between two numbers?+
Take the absolute difference, divide by the average of the two absolute values, and multiply by 100. For 50 and 70: 20 / 60 × 100 = 33.33%.
When should I use percent difference?+
When neither value is the reference: comparing two measurements of the same thing, two competing prices, or results from two groups.
Can percent difference be negative?+
No. It uses absolute values, so it is always 0% or positive. Use percent change if you need to show direction.
Can percent difference be more than 100%?+
Yes, when the values are more than three times apart. 10 and 50 give 133.33%. A ratio is usually clearer in that case.
How is percent error different?+
Percent error divides by an accepted or true value. Use it when one of the two numbers is known to be correct.
About this calculator
- Written by
- mathcheck editorial team
- Last reviewed
- September 4, 2026
Method
- Uses the values entered by the user and stable formulas documented on the page.
Related calculators
Percentage Change Calculator
Find percentage increase or decrease between an original value and a new value with signed change, absolute change, and steps.
Percent Error Calculator
Calculate percent error from experimental and accepted values with absolute error, signed error, and step-by-step substitution.
Percentage Increase Calculator
Increase a number by a percent, find the percent increase between two values, or work backwards from the final value to the original, with the multiplier, increase amount, and step-by-step formulas.
Percentage Decrease Calculator
Reduce a number by a percent, find the percent decrease between two values, or reverse a decrease to recover the original amount, with the multiplier, amount removed, and the percent remaining.
Percentage Calculator
Calculate percent of a number, part-to-whole percentages, percent change, missing wholes, and reverse percent changes.
Average Percentage Calculator
Average a list of percentages correctly: a simple mean when the groups are equal, or a weighted average by sample size when they are not, with both shown side by side and the difference explained.
Last updated: September 4, 2026