Percentage Change vs Percentage Difference: Which One to Use

Use percentage change when one number came first and the other came later, such as an old price and a new price. Use percentage difference when you're comparing two numbers side by side and neither one is the starting point, such as the price of the same item in two shops. For 45 and 60, the change from 45 to 60 is +33.33%, while the percentage difference between them is 28.57%. The Percentage Difference Calculator shows both, plus the plain difference, with every formula written out.

The two formulas

Percentage change = (B − A) ÷ |A| × 100

A is the original value and B is the new one. The result has a sign: positive for an increase, negative for a decrease. Because you divide by A, the order matters.

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

Here the gap is divided by the average of the two values. There's no sign and no starting point, so swapping A and B gives the same answer.

Worked example: same numbers, three answers

Say a monthly subscription went from 45 to 60.

• Absolute difference: |60 − 45| = 15.
• Percentage change, 45 → 60: 15 ÷ 45 × 100 = +33.33%, an increase.
• Percentage change, 60 → 45: −15 ÷ 60 × 100 = −25.00%, a decrease.
• Percentage difference: 15 ÷ ((45 + 60) ÷ 2) = 15 ÷ 52.5 × 100 = 28.57%, in either order.

The percentage difference lands between the two percentage changes, a neutral middle ground that favours neither value. The calculator also shows B as a percentage of A, which here is 60 ÷ 45 × 100 = 133.33%.

Which one should you use?

Situation	Use	Why
A salary rises from 1,200 to 1,500 a month	Percentage change	There's a before and after: +25%
A sale price drops from 200 to 50	Percentage change	The original price is the base: −75%
Coffee costs 3.60 in one café and 4.20 in another	Percentage difference	Neither shop is the reference: 15.38%
Two lab measurements read 98 and 102	Percentage difference	Both are equally valid readings: 4.00%
Last year's sales vs this year's	Percentage change	Time gives a natural starting point

A quick test: if swapping the two numbers changes the story ("the price went up" becomes "the price went down"), use percentage change. If not, use percentage difference.

When the two numbers are close, the methods agree closely too. For 98 and 102, the change is +4.08% and the difference is 4.00%. When they're far apart, the gap grows: going from 200 to 50 is a 75% decrease, but the percentage difference is 120%.

How to use the calculator

1. Enter Value A, the first or original value.
2. Enter Value B, the second or new value.
3. Choose how many decimal places to show, from 0 to 6. The default is 2.
4. Read the results: the absolute difference, the percentage change from A to B (labelled as an increase, decrease or no change), the symmetric percentage difference and B as a percentage of A.
5. Check the note underneath, which plugs your numbers into each formula.

What happens with zero?

Percentage change from zero is undefined. The formula divides by A, and you can't divide by zero. Going from 0 visitors to 40 is an increase from nothing, which no percentage describes, so the calculator shows "Undefined" and explains why.

The percentage difference still works when only one value is zero. For 0 and 40, it's 40 ÷ 20 × 100 = 200%. In fact, whenever one value is zero and the other isn't, the difference is always 200%, which tells you very little. In these cases the absolute difference of 40 is the most honest figure to report. If both values are 0, the percentage difference is undefined as well.

What about negative numbers?

Percentage change divides by |A|, the size of A without its sign. That keeps the direction correct: moving from −20 to −10 is (−10 − (−20)) ÷ 20 × 100 = +50%, because −10 is higher than −20. Without the absolute value, you'd get −50% and call a rise a fall.

When A and B have opposite signs, both percentages get strange. Going from −10 to 30 is a +400% change and a 200% difference. The calculator adds a note in this case, and the absolute difference of 40 is usually the clearer number to share.

Related calculators

For other everyday percentage questions, such as "what is 15% of 80?", use the Percentage Calculator. To apply a rise or a cut to a number, the Percentage Increase Calculator does that directly. If you'd rather express two quantities as a simplified ratio such as 3:4, try the Ratio Calculator. And the Average Calculator finds the mean of a longer list of values.

FAQ

Is percentage difference the same as percentage error?

No. Percentage error compares a measured value with a known true value, dividing by the true value, so it works like percentage change. Percentage difference is for two values where neither is known to be correct.

Can a percentage difference be more than 100%?

Yes. For two positive values, the difference passes 100% once one is more than three times the other. For 10 and 50, it's 40 ÷ 30 × 100 ≈ 133.33%.

Try your own pair in the Percentage Difference Calculator and compare all three answers at once.