Percentage Difference Calculator
A symmetric comparison, where neither value is the reference.
Work out Percentage Difference. A symmetric comparison, where neither value is the reference. Says where the rule comes from.
Percentage difference
40.00%
100 → 150, a increase
Percentage difference has no direction — it divides by the average of the two values rather than by one of them, so swapping the inputs gives the same answer. That makes it the right measure when neither value is the reference, and it is why it reads 40.00% where a one-directional change reads 50.00%.
How the Percentage Difference Calculator works
Percentage difference divides by the average of the two values rather than by one of them, so swapping the inputs gives the same answer. That makes it the right measure when neither value is the baseline — comparing two measurements, two suppliers, two results.
Also known as: percent difference formula · relative difference calculator · percent difference vs percent change · difference between two values as a percentage
Frequently asked questions
What is percentage difference?
The gap between two values divided by their average, as a percentage. Between 100 and 150 it is 40%, where the one-directional change would read 50%.
How is it different from percentage change?
Change has a direction and a baseline; difference has neither. Change from 100 to 150 is +50% while 150 to 100 is −33.3%, but the percentage difference is 40% either way.
When should I use percentage difference?
When neither value is 'first' — comparing two independent measurements, two competing quotes, or two lab results. If one value is genuinely a starting point, use percentage change instead.
Why divide by the average?
To make the measure symmetric. Dividing by either value alone would give a different answer depending on which you picked, which is exactly what this measure avoids.
Put this calculator on your own site
Free to use, on any site, commercial or not. Paste this where you want it to appear. It is a plain iframe, so it works in WordPress, Squarespace, Wix, Webflow, Ghost and anything else that accepts HTML.
<iframe src="https://www.thecalclibrary.com/embed/percentage-difference-calculator" width="100%" height="640" style="border:1px solid #e2e8f0;border-radius:12px" loading="lazy" title="Percentage Difference Calculator"></iframe>The only condition is that the credit line stays visible. It sits inside the frame, so you do not have to do anything to keep it.
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