How to Calculate Percentage Difference
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Direct answer
Take the absolute gap between two peer values and divide by their average magnitude. This answers how far apart the values are relative to a shared scale.
Formula and method
|A−B| / ((|A|+|B|)/2) × 100
The calculation keeps full precision through the formula and rounds only the displayed answer.
Step-by-step calculation
- Confirm neither value is the designated baseline.
- Use the same units.
- Calculate the absolute gap.
- Calculate the average magnitude and divide.
Worked examples
12 and 15
Gap 3, average 13.5, difference 22.222…%.
120 and 100
Gap 20, average 110, difference 18.1818…%.
Order
Reversing either pair leaves the result unchanged.
Interpretation and edge cases
- Some disciplines use a reference or control denominator instead; then the calculation is relative difference or percent error, not this symmetric formula.
- Document the formula in reports.
- Round only at the end.
Frequently asked questions
Which value is the denominator?
Neither alone; use their average magnitude.
Why absolute values?
They prevent sign cancellation in the scale denominator.
Can I compare dollars and euros directly?
Only after converting them to a common unit and time basis.
Sources and transparency
The formulas and examples were evidence-checked on 2026-09-10. This is educational mathematical content. It does not replace a field-specific standard, accounting policy, laboratory method, contractual definition or professional judgment.
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