Calculators & everyday math
Percent Change vs. Percent Difference
Percent change and percent difference both compare two numbers as a percentage, so they are easy to confuse. The difference is whether one of the numbers is a starting point. This guide explains both formulas, when each applies, and where percentage points fit in.
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Percent change: from a starting point
Use percent change when one value came first — an old price and a new one, last year and this year. It divides by the original value, so direction matters: 100 to 125 is +25%, and 125 to 100 is −20%.
Percent difference: two values side by side
Use percent difference when neither value is a starting point — two shops’ prices for the same item, or two measurements of the same thing. It divides the gap by the average of the two values, so the order doesn’t matter:
percent difference = |a − b| ÷ ((a + b) ÷ 2) × 100
For 100 and 125 the gap is 25 and the average is 112.5, so the percent difference is 25 ÷ 112.5 × 100 ≈ 22.22%, whichever value you list first.
Side by side
| Values | Percent change (first → second) | Percent difference |
|---|---|---|
| 100 and 125 | +25% | 22.22% |
| 125 and 100 | −20% | 22.22% |
| 40 and 60 | +50% | 40% |
| 200 and 50 | −75% | 120% |
Percentage points
When both numbers are themselves percentages there is a third comparison: the plain gap in percentage points. A pass rate rising from 60% to 75% is up 15 percentage points, a 25% increase as a percent change, and a 22.22% percent difference.
Which one to use
- There is a before and an after: percent change.
- Two comparable values with no natural order: percent difference.
- Two percentages: state the gap in percentage points, and add the percent change if it helps.
Change vs. Difference FAQ
- What is the formula for percent difference?
- The absolute difference divided by the average of the two values, times 100: |a − b| ÷ ((a + b) ÷ 2) × 100.
- Why does percent difference give the same answer both ways?
- It divides by the average of the two values, which doesn’t change when you swap them.
- Can percent difference be more than 100%?
- Yes, when the values are far apart: 200 and 50 differ by 120%. For two positive values it always stays below 200%.
- Which one should I use for a price increase?
- Percent change, because there is a clear before and after.
- What is a percentage point?
- The plain difference between two percentages: 60% to 75% is 15 percentage points.
Related guides
- Calculate Percentage ChangeThe percentage change formula with worked examples, how to read positive and negative results, a spreadsheet formula, and checks that catch errors.
- Change From Zero or NegativeWhy percentage change from zero is undefined, why a negative starting value can flip the sign, and how to report these changes honestly.
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