Percentage Difference: Your Questions Answered
These are the questions people ask most often about percentage difference. Each answer is short; follow the links for the full detail.
What does a percentage difference calculation tell me?
Compares two values relative to their average.
What is the formula?
% diff = |A − B| ÷ ((A + B) ÷ 2) × 100.
What do I need to enter?
Value A, Value B.
Can I use any units?
Yes, as long as every input uses the same unit. The answer will be in that unit (squared for areas, cubed for volumes).
Can you show an example?
For example, with these inputs:
- Value A: 40
- Value B: 50
the calculator returns:
- Percentage difference: 22.22%
Any tips?
- Check your answer by working backwards from the result.
- Estimate the answer roughly first so you can spot a result that is clearly wrong.
- When numbers are very large or small, scientific notation makes them easier to compare.
Background
These calculations appear throughout the Singapore syllabus, from primary school percentages and fractions to secondary school algebra and geometry. Understanding the formula makes problem sums easier because you can recognise which quantity is missing.
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.
Calculators are best used to check working rather than replace it, especially for exams where method marks count. Work the problem by hand first, then confirm with the calculator.
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.
Try it yourself with the Percentage Difference Calculator.
Run your own numbers: Percentage Difference Calculator