Percentage Difference vs Percentage Change
They are not the same formula, and mixing them up produces wrong answers. Percentage change has a clear "before" and "after." Percentage difference compares two values as peers, with no starting point. This guide explains both, shows the formulas, and walks through when to use each.
The Core Distinction
A value moved from point A to point B. You measure how much it moved relative to where it started. The result can be positive (up) or negative (down).
Two values exist side by side. Neither is the "original." You measure how far apart they are relative to their average. The result is always positive.
The Formulas
Percentage Change
Percentage Change = (New minus Old) / Old x 100
Use this when one value came first and the other came after.
Example: A stock was $40. Now it is $52. Percentage change: (52 minus 40) / 40 x 100 = 30% increase.
Percentage Difference
Percentage Difference = |A minus B| / ((A + B) / 2) x 100
Use this when you are comparing two equal-status values and there is no "starting point."
The denominator is the average of both values, which keeps the formula symmetric. Swap A and B and you get the same answer.
Example: Store A sells the same jacket for $80; Store B sells it for $100. Percentage difference: |80 minus 100| / ((80 + 100) / 2) x 100 = 20 / 90 x 100 = 22.2%.
Why the Answers Differ
Compare: a salary of $60,000 vs $75,000.
Percentage change from $60K to $75K: (75,000 minus 60,000) / 60,000 x 100 = 25%.
Percentage change from $75K to $60K: (60,000 minus 75,000) / 75,000 x 100 = minus 20%.
Percentage difference: |60,000 minus 75,000| / ((60,000 + 75,000) / 2) x 100 = 15,000 / 67,500 x 100 = 22.2%.
Three different numbers from the same two values, depending on the question. Which is correct depends entirely on what you are trying to say.
When to Use Each
| Situation | Use |
|---|---|
| Revenue this year vs last year | Percentage Change |
| Prices at two competing stores | Percentage Difference |
| A student's score before and after tutoring | Percentage Change |
| Test results from two different groups | Percentage Difference |
| Your salary compared to a colleague's | Percentage Difference |
| A share price from January to December | Percentage Change |
| Energy use in two similar buildings | Percentage Difference |
Ask: is one value clearly the "starting point"? If yes, use percentage change. If the two values are on equal footing, use percentage difference.
A Common Mistake: Using Percentage Change Asymmetrically
A price falls from $100 to $75, a 25% decrease. It later rises back from $75 to $100, a 33.3% increase. Same two prices, but the percentage is different each direction. People sometimes quote the larger number when they want to emphasise a rise, or the smaller when they want to downplay a fall. If you see percentage change used in a context where both directions should be equivalent, percentage difference is probably the fairer measure.
Percentage Points: A Third Concept
Neither percentage change nor percentage difference is the same as percentage points. A percentage point is the raw arithmetic difference between two percentage values. If unemployment falls from 6% to 4%, it fell by 2 percentage points. The percentage change in the unemployment rate is (4 minus 6) / 6 x 100 = minus 33.3%. Both statements are true; they measure different things.
Media coverage often blurs these three. The article on common percentage mistakes covers this and other easy-to-miss errors in more detail.
Worked Examples Side by Side
| Question | Formula | Answer |
|---|---|---|
| Product sold for $50 last month, $65 this month | Change: (65-50)/50 x 100 | 30% increase |
| Product A costs $50, Product B costs $65 | Difference: 15/57.5 x 100 | 26.1% |
| Team A scored 420 points, Team B scored 380 | Difference: 40/400 x 100 | 10% |
| Revenue rose from 380 to 420 over a quarter | Change: (420-380)/380 x 100 | 10.5% increase |
Related Guides
For the percentage change formula in detail: percentage change between two numbers. For an increase specifically: percentage increase calculator. And the percentage calculator on the homepage handles percentage change under its third tool.
Frequently Asked Questions
What is the difference between percentage difference and percentage change?
Percentage change compares a new value to a specific starting point. Percentage difference compares two values without a defined before and after, using their average as the reference.
What is the formula for percentage difference?
Percentage Difference = |Value A minus Value B| / ((Value A + Value B) / 2) x 100. The result is always positive because there is no direction.
When should I use percentage difference instead of percentage change?
Use percentage difference when comparing two peers, such as prices at two stores or test results from two groups. Use percentage change when one value clearly came before the other.
Can percentage difference give a different answer if I swap A and B?
No. Percentage difference is symmetric. Swapping A and B gives the same result because the formula uses the absolute difference and the average of both values.