Percentage Difference Calculator

Percentage Difference Calculator compares two values with the symmetric formula |A − B| ÷ ((|A| + |B|) ÷ 2) × 100. It shows the absolute difference, the average magnitude and the percentage difference, with every step written out. Because neither value is treated as the starting point, swapping A and B gives the same answer.

When two measurements have no natural “before” and “after” — two lab readings, two suppliers’ prices, two survey results — percentage change would give different answers depending on which you divide by. Percentage difference compares them evenly.

1. Enter Value A.
2. Enter Value B — the order does not matter.
3. Press Calculate difference.
4. Read the percentage difference, absolute difference and average magnitude, and check the working.
5. Copy or download the summary, which includes the formula and every step.

• Symmetric percentage difference formula, clearly stated
• Absolute difference and average magnitude shown alongside the result
• Positive, negative and decimal values (up to 10 decimal places)
• Exact decimal arithmetic; the percentage is rounded to 6 decimal places and marked when rounded
• Clear explanation when both values are 0 and the result is undefined
• Step-by-step working in the page, the copied text and the download

• Use percentage change instead when one value is clearly the original and the other the new value.
• Keep both values in the same unit before comparing them.
• Remember that the result can never exceed 200%, which is reached when one value is 0 or the signs are opposite and equal.
• Report the absolute difference too — a large percentage can hide a tiny absolute gap between small numbers.