Percentage Difference Calculator
Need to compare two numbers but don’t want to treat one of them as the original or starting value?
Use this Percentage Difference Calculator to find the percentage difference between two values instantly. Enter the two numbers, and the calculator determines their absolute difference, average, and percentage difference.
Whether you’re comparing measurements, test results, prices, experimental data, statistics, or two sets of values, this tool gives you a quick way to see how far apart the numbers are.
Percentage Difference Calculator
Compare two numbers using their average as the reference point. Get the percentage difference, absolute difference, and average instantly.
The two values have a 0% difference.
What Is Percentage Difference?
Percentage difference describes how different two values are from each other when neither value is treated as the starting point.
This makes it useful when you simply want to compare two measurements or numbers rather than describe an increase or decrease.
For example, suppose two measurements are 80 and 100.
Their absolute difference is:
|80 − 100| = 20
Their average is:
(80 + 100) ÷ 2 = 90
So the percentage difference is:
20 ÷ 90 × 100 = 22.22%
The percentage difference between 80 and 100 is therefore 22.22%.
The important point is that the average of the two values is used as the reference in this calculation.
Percentage Difference Formula
If your two values are A and B, use:
Percentage Difference = |A − B| / [(A + B) / 2] × 100
There are three parts to the calculation:
- Find the absolute difference between the two numbers.
- Find their arithmetic average.
- Divide the difference by the average and multiply by 100.
The absolute value makes the result non-directional. In other words, switching the order of the two numbers does not change the percentage difference.
A quick example
For values of 25 and 35:
- Difference = |25 − 35| = 10
- Average = (25 + 35) ÷ 2 = 30
- Percentage difference = 10 ÷ 30 × 100
- Percentage difference = 33.33%
Percentage Difference vs. Percentage Change
This is one of the most common sources of confusion.
Percentage difference is appropriate when you’re comparing two values and neither one is designated as the original value.
Percentage change is used when there is a clear starting value and a later value. The difference is then measured relative to the starting value.
For example, if a price changes from $50 to $60, the percentage change is calculated using $50 as the starting point:
($60 − $50) ÷ $50 × 100 = 20%
But if you’re simply comparing $50 and $60 without calling either one the starting value, the percentage difference is:
$10 ÷ $55 × 100 = 18.18%
So the two calculations answer different questions.
| Question | Calculation |
|---|---|
| How much did the value increase or decrease? | Percentage change |
| How different are these two values? | Percentage difference |
| Which value was the starting value? | Needed for percentage change |
| Is either value the reference? | No for percentage difference |
How to Calculate Percentage Difference by Hand
You don’t need a calculator to understand the calculation.
Suppose you want to compare 120 and 150.
Step 1: Find the difference
|120 − 150| = 30
Step 2: Find the average
(120 + 150) ÷ 2 = 135
Step 3: Divide the difference by the average
30 ÷ 135 = 0.2222
Step 4: Convert to a percentage
0.2222 × 100 = 22.22%
Therefore:
The percentage difference between 120 and 150 is approximately 22.22%.
When Should You Use Percentage Difference?
Percentage difference is useful when two values represent measurements or observations that you want to compare on a relative scale.
You might use it for:
- Comparing two experimental measurements
- Comparing two test results
- Checking differences between calculated values
- Comparing prices or estimates
- Comparing measurements from different sources
- Comparing two statistical values
- Checking how closely two results agree
- Comparing readings from different instruments
- Comparing two quantities when there is no defined starting value
It can be particularly convenient when saying “X increased from A to B” doesn’t accurately describe the situation.