Algebra Percent Difference

Frequently asked questions

• What is percent difference?

  Percent difference compares two numbers against their average, not against just one of them. The formula is |A − B| ÷ ((|A| + |B|) / 2) × 100. For 50 and 60, the result is about 18.18%.

• Is percent difference the same as percent change?

  No. Percent change from 50 to 60 is (60 − 50) / 50 × 100 = 20%. Percent difference uses the average of 50 and 60 as the base, so it is 10 / 55 × 100 ≈ 18.18%. Use percent change when one value is the starting point.

• Does the order of A and B matter?

  No. The formula uses absolute values, so 50 and 60 give the same percent difference as 60 and 50. There is no positive or negative direction.

• Can the result be more than 100%?

  Yes. 0 and 10 give 200%, because the gap is twice their average. The circle stops at 100% only as a visual scale. The percent shown in the result is not capped.

• What happens if both numbers are zero?

  The difference is 0, so the percent difference is 0%. If only one number is zero, the result is 200%, because the average is half of the non-zero number.

• When should I use this?

  Use it when neither number is the official starting value, such as two lab readings, two quoted prices, or two estimates. If you are measuring growth from an old value to a new value, percent change is the better formula.