Percentage Calculator
Work out a percentage of an amount, or the percentage change between two numbers.
Result
25
- 10% of 250
- 25
How it's calculated
- X% of Y: divide X by 100, then multiply by Y. In short, X ÷ 100 × Y.
- Percentage change from X to Y: subtract X from Y, divide by X (the starting number), then multiply by 100. A positive result is an increase and a negative result is a decrease.
- If the starting number X is 0, the percentage change cannot be worked out, so the calculator shows 0%.
- To take a percentage off a price, work out that percentage of the price and subtract it. To add a percentage, add the amount instead.
Worked examples
15% of $240
15 ÷ 100 = 0.15, and 0.15 × 240 = 36. So 15% of $240 is $36.
A price drop from $80 to $68
68 − 80 = −12. Then −12 ÷ 80 = −0.15, and −0.15 × 100 = −15. The price fell by 15%.
20% off a $65 shirt
20 ÷ 100 × 65 = 13, so the discount is $13. The sale price is 65 − 13 = $52.
Assumptions and notes
- Standard arithmetic — no Australian-specific rules apply.
Information last checked: October 2026.
Frequently asked questions
How do I calculate a percentage increase?
Subtract the old number from the new number, divide by the old number and multiply by 100. Going from 50 to 65 is (65 − 50) ÷ 50 × 100 = 30%.
Is the change from A to B the same as from B to A?
No, because the starting number is different. Going from 100 to 120 is a 20% increase, but going from 120 back to 100 is a decrease of about 16.67%.
Can I use this to work out GST?
For a quick sum, yes. GST in Australia is 10%, so 10% of $55 is $5.50. For GST-inclusive and GST-exclusive prices, use the GST calculator.