Calculate the percentage difference between two values, a symmetric comparison that treats neither value as the reference or 'correct' one.
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Percentage Difference = |A − B| ÷ ((A + B) ÷ 2) × 100, dividing the absolute difference by the average of the two values rather than by either one specifically. This symmetry means swapping A and B gives the exact same result, unlike percentage change, which is directional and depends on which value is treated as the starting point.
Use percentage difference when comparing two values as equal peers, neither is a 'before' state nor a known correct standard, for example, comparing two competitors' prices, or two lab samples measured under similar conditions. If one value is a starting point being changed into another (like a salary before and after a raise), our Percentage Calculator's percentage change mode is more appropriate. If one value is a known accepted standard being checked against a measurement, use our Percent Error Calculator instead.
Dividing by the average keeps the calculation symmetric, giving the same result regardless of which value you call 'first' or 'second', appropriate when neither value is inherently the reference point.
No, this calculator uses the absolute difference in the numerator, so percentage difference is always reported as a non-negative magnitude of how far apart the two values are, not a directional change.
This calculator expects non-negative values, since the standard percentage difference formula is best defined for positive quantities. For values that can be negative or represent a directional change, percentage change (available in our Percentage Calculator) is more appropriate.
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