Percentage Difference Calculator
The symmetric percentage difference between two values, plus the change in each direction.
Results
What this tool does
There are two different questions hiding behind the phrase "what is the percentage difference", and picking the wrong one is one of the most common quiet errors in a report. If one value came before the other, you want percentage change and it matters which is which. If the two values are simply two readings — two labs, two instruments, two quotes — then neither is the baseline, and dividing by their average is the only treatment that does not favour one over the other. This page gives you all three numbers so the choice is in front of you.
Formula
percent difference = |a - b| / ((a + b) / 2) x 100
Variables
| Symbol | Meaning | Unit |
|---|---|---|
va | First value | — |
vb | Second value | — |
PD | Percentage difference | % |
DF | Difference | — |
AV | Average order value | — |
CA | Change from A to B | % |
CB | Change from B to A | % |
Worked example
- First value40
- Second value60
- Percentage difference40.0000 %
- Difference20.0000
- Average order value50.0000
- Change from A to B50.0000 %
- Change from B to A-33.3333 %
Limitations
- The calculation runs at full precision and only the display is rounded. If you copy an intermediate value and retype it, small differences can appear.
Frequently asked questions
How is this different from percentage change?
Percentage change has a direction: it measures from a starting value to a later one, and swapping the two gives a different answer. Percentage difference has no direction — it compares two values that are simply both there, like two measurements of the same thing or two suppliers' prices, and it divides by their average so that swapping them changes nothing. From 40 to 60 is a 50% increase, but the percentage difference between 40 and 60 is 40% whichever way round you enter them.