Percentage Difference (and How It Differs From Change)
What percentage difference means, its formula, and how it differs from percentage change — with worked examples.
Want to crunch a percentage right now?
Open the Percentage Calculator →More percentage guides
Frequently asked questions
How do I calculate percentage difference?
Take the absolute difference of the two values, divide by their average, and multiply by 100.
How is percentage difference different from percentage change?
Difference compares two equal-status values using their average as the base and is symmetric; change compares a new value to an original and has direction.
Does the order of the two numbers matter?
No. Because percentage difference uses the average as the denominator, you get the same result regardless of order.
When should I use percentage difference?
When comparing two independent measurements with no natural starting point, such as two lab readings of the same sample.
Can percentage difference be negative?
No. It uses the absolute value of the gap, so it is always zero or positive.
What if the two values are equal?
The difference is zero, so the percentage difference is 0%.
What percentage difference measures
Percentage difference compares two values when neither is naturally the "starting" one — for example two measurements of the same thing. It uses the formula |a − b| ÷ ((a + b) ÷ 2) × 100, dividing the gap by the average of the two values.
Worked example
For 40 and 60: the difference is |40 − 60| = 20, the average is (40 + 60) ÷ 2 = 50, so the percentage difference is 20 ÷ 50 × 100 = 40%. Because it uses the average as the base, the answer is the same whichever value you list first.
Difference vs change
Percentage difference is symmetric and compares two equal-status values. Percentage change is directional and compares a new value against an original. Use change for "before and after" figures and difference for comparing two independent measurements.
Percentage difference is common in science and quality control — comparing a measured value with a reference, or two readings of the same quantity — where there is no obvious "old" and "new" value.
Results are estimates for general guidance in United Arab Emirates and may not reflect the latest local rates, fees or rules. Check official sources before making decisions.