Percentage Difference Calculator

1. Find the absolute difference between the two values.
2. Calculate the average of the two values.
3. Divide the absolute difference by the average, then multiply by 100.

Example: Value 1 = 100, Value 2 = 120. Absolute difference = |100 − 120| = 20. Average = (100 + 120) ÷ 2 = 110. Percentage difference = 20 ÷ 110 × 100 ≈ 18.18%.

Percentage Difference = |Value 1 − Value 2| ÷ ((Value 1 + Value 2) ÷ 2) × 100

Example 1: Value 1 = 100, Value 2 = 120. Absolute difference = 20, average = 110, percentage difference = 20 ÷ 110 × 100 ≈ 18.18%.

Example 2: Value 1 = 50, Value 2 = 70. Absolute difference = 20, average = 60, percentage difference = 20 ÷ 60 × 100 ≈ 33.33%.

Percentage difference uses the average of the two values as the reference denominator, so it treats both values symmetrically — it doesn't matter which one you enter first. Percentage change uses the original/reference value as the denominator, so it matters which value is the "before" and which is the "after." If you're tracking a value increasing or decreasing over time from a known starting point, percentage change is usually the more appropriate calculation.

Percentage difference is useful any time you want to compare two numbers without designating one as the "correct" or "starting" value. For example, comparing two competitors' prices, two survey results, or two measurements taken under similar conditions.

Example: two stores price the same item at $45 and $50. Absolute difference = $5, average = $47.50, percentage difference = 5 ÷ 47.50 × 100 ≈ 10.53%.

Percentage difference can be useful when comparing two experimental or measured values when neither one is treated as the accepted or reference value — for example, comparing two independent measurements of the same quantity. If one value is a known, accepted, or target value, a percentage change or percentage error calculation relative to that value is typically more appropriate than percentage difference.