=AllInOneCalculator

Percentage Difference Calculator

Compare two values symmetrically. Percentage difference divides the absolute gap by the average of the two values.

Percentage difference
22.22%
Absolute difference20.00
Average of A and B90.00
Larger valueValue B
Formula|A − B| ÷ avg × 100
Rounded to 2 decimals.
Results update as you type

What this calculator does

This calculator answers how different are these two values when neither one is the baseline — for example, comparing two products, two test results, or two cities. If one value comes first in time, use the Percentage Increase or Percentage Decrease calculator instead.

Formula

% difference = |A − B| ÷ ((A + B) ÷ 2) × 100

Variable definitions

  • A — First value being compared.
  • B — Second value being compared.
  • |A − B| — Absolute difference — always non-negative.
  • (A + B) ÷ 2 — Arithmetic average of the two values, used as the denominator.

Step-by-step calculation

  1. Subtract: A − B, then take the absolute value.
  2. Average the two values: (A + B) ÷ 2.
  3. Divide step 1 by step 2.
  4. Multiply by 100 to get a percentage.

Worked example

Compare two prices: A = $80, B = $100.

  • |80 − 100| = 20
  • (80 + 100) ÷ 2 = 90
  • 20 ÷ 90 = 0.2222
  • × 100 = 22.22% percentage difference

How to use this calculator

  1. Enter value A and value B.
  2. Read the percentage difference, the absolute gap, and the average.
  3. Switch to Increase or Decrease if one value is clearly the baseline.

Common mistakes

  • Mixing up difference and change: percentage difference is symmetric; percentage change is not.
  • Dividing by the smaller value: the denominator is the average, not the minimum.
  • Mixed signs: if A and B have opposite signs the average can be zero or near zero, making the result meaningless.

Frequently asked questions

›What is percentage difference?

Percentage difference compares two values without treating either as the 'original'. It divides the absolute difference by the average of the two values, then multiplies by 100.

›How is it different from percentage change?

Percentage change (increase or decrease) uses one value as the baseline. Percentage difference is symmetric — swapping A and B gives the same answer. Use change when one value comes first in time; use difference when comparing two peers.

›What is the formula?

|A − B| ÷ ((A + B) ÷ 2) × 100. The result is always non-negative.

›Can both values be negative?

The formula assumes both values are positive (or have the same sign). For mixed signs the average can be zero or change sign, which makes the result undefined or misleading.

›What if both values are equal?

The difference is 0% — the two numbers are identical.

›Why does the result feel smaller than I expected?

Because the denominator is the average, not the smaller value. 80 vs 100 is 22.2% difference, but a 25% increase from 80 to 100 or a 20% decrease from 100 to 80.

›Is percentage difference the right tool for my data?

Use it when neither value is a baseline (e.g. comparing two products, two cities, two measurements). For before/after comparisons use Percentage Increase or Decrease instead.

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Last updated: June 22, 2026 · Checked against standard formulas and sample test cases. Result is symmetric: |A − B| / ((A + B) / 2) × 100. Display rounded to two decimals.