Calculate the percentage difference between two values, a symmetric comparison that treats neither value as the reference or 'correct' one.
Google AdSense Banner
This area will contain advertisements after approval.
Google AdSense Banner
This area will contain advertisements after approval.
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.
Comparing two values, 40 and 50: the absolute difference is |40 − 50| = 10, and the average of the two is (40 + 50) ÷ 2 = 45. Percentage difference = (10 ÷ 45) × 100 ≈ 22.22%. Notice this differs from a percentage change from 40 to 50, which would be (10 ÷ 40) × 100 = 25%, because percentage change divides by the starting value specifically rather than the average of both.
Confusing percentage difference with percentage change, percentage difference divides by the average of both values and is symmetric (order doesn't matter), while percentage change divides by the starting value specifically and is directional, these can give noticeably different results for the same two numbers.
Treating percentage difference as capable of showing direction (increase vs decrease), it can't, the result is always a non-negative magnitude of how far apart two values are, not which one is bigger.
Using this calculator when one value is actually a known correct standard, in that case percent error (dividing by the accepted value specifically) is the more appropriate and conventional choice.
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.
Google AdSense Banner
This area will contain advertisements after approval.