The percentage difference between 80 and 100 is 22.22%.
Show calculation steps
- |80 − 100| = 20.
- Average = (|80| + |100|) ÷ 2 = 90.
- Difference ÷ average × 100 = 22.2222%.
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Compare two supplier quotes
Quote A: 80 · Quote B: 100
- 01
Find the gap: |80 − 100| = 20.
- 02
Average the two values: (80 + 100) ÷ 2 = 90.
- 03
Divide by the average: 20 ÷ 90 × 100 ≈ 22.22%.
Illustrative example · Neither quote is the starting value. If you want the increase from 80 to 100, use percentage change instead.
Load this example ↗Formula & method
Percentage difference is best when two measurements are peers. If one value is explicitly old and the other is new, percentage change is usually the better calculation.
Difference, change and percentage points
Two independent measurements of 80 and 100 differ by 20. Their average is 90, giving a percentage difference of about 22.22%. Swapping the inputs leaves this result unchanged.
If 80 is an earlier value and 100 is a later value, the question is instead about growth: the percentage change is 25%. If both numbers represent rates, a percentage-point comparison may be more useful.
How zero and negative inputs are handled
This tool uses the average of the absolute input values as its denominator. For nonnegative values this is the ordinary arithmetic average. One zero and one nonzero value give 200%; two zeros give an undefined result. Opposite signs also give 200% under this convention, so interpret signed measurements carefully.
Use comparable measurements
Convert inputs to the same units first. Comparing 1 metre with 100 centimetres directly would be misleading; both should be entered as 1 metre or 100 centimetres. Displayed percentages are rounded, so small differences may disappear at the displayed precision.
Frequently asked questions
Does order matter for percentage difference?
No. Swapping the two values produces the same percentage difference.
When should I use percentage change instead?
Use percentage change when one value is the starting or original value and the other is the ending value.