Compare two numbers symmetrically when neither value is the original or starting value.
How it works
The formula shows how the percentage difference calculator turns your inputs into the result. Use it to check the calculation, then follow the example steps to see each part of the math.
D% = |A - B| / ((|A| + |B|) / 2) x 100
Use this to compare two values without treating either one as the original value.
D%= Percentage differenceA, B= The two values being compared|A - B|= Absolute difference between the values(|A| + |B|) / 2= Average size of the two valuesCompare measurements of 80 and 100
Find the absolute difference
|80 - 100| = 20
Find their average
(80 + 100) / 2 = 90
Divide and convert to a percent
20 / 90 x 100 = 22.22%
Compare quotes of $50 and $60
Find the absolute difference
|$50 - $60| = $10
Find their average
($50 + $60) / 2 = $55
Divide and convert to a percent
$10 / $55 x 100 = 18.18%
Spreadsheet formulas
Enter the example values in the listed cells, then paste the formula into another cell. Excel and Google Sheets use the same formulas shown here.
| Cell | Meaning | Example value |
|---|---|---|
| A2 | First value | 80 |
| B2 | Second value | 100 |
Formula
=ABS(A2-B2)/AVERAGE(ABS(A2),ABS(B2))Expected result: 22.22%
Format the result cell as a percentage. At least one value must be different from zero.
Percentage difference guide
The correct comparison depends on whether either value is a starting point. Percentage difference is symmetric; percentage change is directional.
Use the average of the two values as the denominator when comparing measurements, quotes, or results where neither value is the original. Swapping the inputs does not change the answer.
When one value came first, divide the change by that old value. This produces a directional result and can differ from percentage difference.
Calculate old-to-new percentage change →If both values are zero, the average is zero and percentage difference is undefined. If only one value is zero, the symmetric formula returns 200%.
Use percentage difference when comparing two values and neither one is clearly the original or starting value.
The average gives a neutral reference point, so the result is the same no matter which value you enter first.
Percentage difference compares two values symmetrically using their average. Percentage change compares a new value with a specific old value.
The percentage difference is undefined because both the difference and average are zero. If only one value is zero, this formula gives 200%.
Yes. This calculator uses absolute magnitudes in the average. A comparison involving negative values or opposite signs can be mathematically valid but may need the original signed values for context.
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