The formula
Subtract one value from the other, take the size of the gap, divide by the average of the two values, then multiply by 100.
Because the base is the average, swapping the two values gives the same answer.
Worked example
Compare 120 and 150. The gap is 30 and the average is 135, so 30 / 135 x 100 = 22.2222%.
Entering 150 and 120 gives the same 22.2222%, because the gap and the average are unchanged.
When to use it
Use percentage difference when neither value is a baseline, such as comparing two measurements of the same thing or two quotes for the same job.
Use percentage change when one value clearly came first, because that method divides by the earlier value instead.
Inputs for the percentage difference calculator
First value
One of the two numbers you are comparing. The order does not change the answer.
Second value
The other number. If the two values cancel out to an average of zero, there is nothing to divide by.
CALCULATOR QUESTIONS
Percentage difference calculator questions
What is the percentage difference between 120 and 150?
22.2222%. The gap is 30, the average is 135, and 30 / 135 x 100 = 22.2222%.
Does the order of the values matter?
No. The method uses the size of the gap and the average, so both orders give the same percentage.
What is the difference from percentage change?
Percentage change divides by the original value. Percentage difference divides by the average of the two values, so neither is treated as the base.
Can the answer be more than 100%?
Yes, when one value is negative. Comparing 100 with -50 gives a gap of 150 and an average of 25, which is 600%.