Percentage Difference Formula Explained, With Examples
Every percentage difference result comes from one formula. Once you understand what goes into it, you can sanity-check any figure you are given, whether by an employer, a bank, a teacher or another website.
The formula
% diff = |A − B| ÷ ((A + B) ÷ 2) × 100.
What each input means
- Value A: the value you enter in the calculator.
- Value B: the value you enter in the calculator.
Example
For example, with these inputs:
- Value A: 40
- Value B: 50
the calculator returns:
- Percentage difference: 22.22%
How the result changes
The table keeps the other inputs at their example values and changes value a.
| Value A | Percentage difference |
|---|---|
| 40 | 22.22% |
| 20 | 85.71% |
| 30 | 50.00% |
| 50 | 0.00% |
| 60 | 18.18% |
Why it matters
These calculations come up in school, at work and in daily life, from PSLE and O-Level practice to measuring a room for new flooring. Doing them by hand builds understanding, and a calculator lets you check the answer instantly.
Rounding is a common source of small errors. Keep full precision during intermediate steps and round only the final answer to the number of decimal places or significant figures the question asks for.
A quick mental estimate before calculating is a powerful check. If a room's floor area comes out at 4,000 square metres or a percentage comes out above 100% when it should not, you know to look again.
In everyday life the same maths shows up in discounts, recipe scaling, renovation measurements and comparing prices per unit. Being comfortable with it saves money and avoids costly measuring mistakes.
Related calculations
- Average (Mean) Calculator: Finds the arithmetic mean of a list.
- Median Calculator: Finds the middle value of a list.
- Mode Calculator: Finds the most frequent value(s).
- Range Calculator: Finds the spread between the largest and smallest value.
Use the Percentage Difference Calculator to plug in your own numbers.
Run your own numbers: Percentage Difference Calculator