Percentage Difference Calculator
Compare two values without treating either one as the original. Percentage difference uses the average of both values as the reference.
- Absolute Difference
- 20
- Average
- 50
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The result is always nonnegative and remains the same if A and B are swapped.
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How to Use This Calculator
Enter two nonnegative values. If both values are zero, this calculator returns 0% by convention because the values are identical.
Formula & Methodology
Percentage Difference = |A − B| ÷ ((A + B) ÷ 2) × 100. To avoid an undefined 0 ÷ 0 case, two zero inputs are treated as a 0% difference.
Example: compare 40 and 60
The absolute difference is 20, the average is 50, and the percentage difference is (20 ÷ 50) × 100 = 40%.
This version accepts nonnegative values. If both values are zero, it returns 0% by explicit convention. Use Percentage Change when one value is the original and direction matters.
Percentage difference is a descriptive comparison. A field-specific method may use a different denominator or tolerance rule.
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Related Guides
- Percentage Difference vs. Percentage Change: What's the Difference?Percentage difference and percentage change are not the same thing. Learn when to use each, how to calculate both, and why the distinction matters in data analysis and everyday math.
- What Is Percentage Increase? Formula, Examples, and Common UsesUnderstand percentage increase: the formula, how to calculate it step by step, and real-world examples in prices, salaries, and test scores. Includes common mistakes to avoid.
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Frequently Asked Questions
- What is the percentage difference formula?
- It is |A − B| ÷ ((A + B) ÷ 2) × 100.
- Why does percentage difference use the average?
- Using the average creates a symmetric reference, so swapping A and B does not change the result.
- What happens when both values are zero?
- The standard expression is undefined, but this calculator returns 0% by convention because the values are identical.
- How is percentage difference different from percentage change?
- Difference is symmetric and has no direction. Change compares a new value with an original value and can be positive or negative.
Last updated 7/17/2026