Everyday & industry
Percentage Difference Calculator
Calculate symmetric percentage difference, compare values and ratios, or compare the percentage difference of two pairs.
Use this calculator to compare two values symmetrically using percentage difference.
Percentage difference does not treat either value as the starting value. It measures the absolute difference relative to the average magnitude of both values.
Use the same unit and basis for every value. Calculations retain full precision; percentages display to two decimals and values and ratios to up to four decimals.
Calculations run locally in your browser. Your inputs are not saved.
Choose how you want to compare values.
About this calculator
Percentage Difference vs. Percentage Change
Percentage difference is symmetric; swapping the two values does not change the result. Percentage change is directional and uses an original or starting value as its reference.
- Percentage difference = |A − B| ÷ ((|A| + |B|) ÷ 2) × 100.
- Percentage change = (New − Original) ÷ Original × 100.
- Both measures use the full precision of the entered values; only displayed results are rounded.
Why Can 0 and 100 Have a 200% Difference?
Percentage difference uses the average magnitude of both values as its denominator. For 0 and 100, that average is 50, so 100 ÷ 50 × 100 = 200%.
Percentage Difference Examples
These static examples are for reference. Your calculated results appear separately after submission.
- 80 and 100: absolute difference 20; average magnitude 90; percentage difference 20 ÷ 90 × 100 = 22.22%.
- 100 and 120: absolute difference 20; average magnitude 110; percentage difference 20 ÷ 110 × 100 = 18.18%.
- −80 and −100: absolute difference 20; average magnitude 90; percentage difference 22.22%.
- 0 and 100: absolute difference 100; average magnitude 50; percentage difference 200%.
Frequently asked questions
What is percentage difference?
Percentage difference expresses the absolute difference between two values as a percentage of their average magnitude. It is symmetric, so swapping the values does not change the result.
What is the formula for percentage difference?
|A − B| ÷ ((|A| + |B|) ÷ 2) × 100. The denominator uses the average of both absolute magnitudes, not the signed arithmetic mean.
What is the difference between percentage difference and percentage change?
Percentage difference compares two values symmetrically using their average magnitude. Percentage change measures a directional change relative to an original or starting value.
Can percentage difference be greater than 100%?
Yes. For example, the difference between 0 and 100 is 100, and their average magnitude is 50. The percentage difference is 100 ÷ 50 × 100 = 200%.
What happens if one value is zero?
The percentage difference is defined when only one value is zero. For 0 and 100, the result is 200%. A ratio or difference relative to the zero value is shown as N/A because it would require division by zero.
What happens if both values are zero?
Their absolute difference is zero, and the percentage difference is 0%. Ratios and differences relative to either value are N/A because both denominators are zero.
Does swapping the values change percentage difference?
No. The absolute difference and average magnitude are symmetric, so percentage difference remains the same when A and B are swapped.
General mathematical comparisons only, not financial or business advice. No accounts, database, AI or external API calls are used. Calculations run locally in your browser and your inputs are not saved.