Percentage calculator
A €80 jacket at 15% off: 15% of 80 is 12, so you pay 68. The second row shows that remaining 68 without a second sum.
A percentage is a fraction out of a hundred. To find X% of a number, multiply by X and divide by 100. To find what percentage one number is of another, divide the first by the second and multiply by 100. Percentage change is the difference divided by the starting value, times 100.
How to use it
Percentage points and per cent are different things, and mixing them up is the most common error in this whole area. If a rate moves from 4% to 5%, that is a rise of one percentage point and a rise of twenty-five per cent. Both statements are true and they are not interchangeable.
Questions
Because the second percentage is taken from a bigger number. Eighty up 25% is 100; a hundred down 25% is 75, not 80. Use the change mode to see it.
Divide rather than subtract. A price including 21% VAT is divided by 1.21 to get the net figure. Subtracting 21% gives a different, wrong answer.
The plain arithmetic difference between two percentages. From 4% to 5% is one percentage point, and also a 25% increase.
Yes, one at a time. Thirty per cent off then a further twenty per cent off is not fifty per cent off: it leaves 56% of the original price.