Percentage & Discount Calculator
Six calculations in one place: a percentage of a number, the change between two numbers, what share one number is of another, a sale price, VAT added, and VAT stripped back out of a gross figure.
Percentage & Discount Calculator
Six calculations in one place: a percentage of a number, the change between two numbers, what share one number is of another, a sale price, VAT added, and VAT stripped back out of a gross figure.
Choose the mode first — the fields change with it, so you are never asked for a number the calculation does not use.
How to read the result
- For "change", the result is relative to the first number. Going from 200 to 250 is a 25 per cent rise; going back from 250 to 200 is a 20 per cent fall. Both are correct, and they are not the same number.
- VAT out is not the same as taking the percentage off. Removing 20 per cent VAT from 120 gives 100, not 96 — the tax was calculated on the smaller figure.
- A percentage of zero has no meaning, so the tool prints a dash rather than inventing a number. If you see one, check which field is empty.
Frequently asked questions
How do I take VAT out of a price that already includes it?
Divide by 1 plus the rate, do not subtract the percentage. At 20 per cent VAT, a gross price of 120 divides by 1.2 to give a net price of 100 and VAT of 20. Subtracting 20 per cent from 120 gives 96, which is wrong by four units and by a whole concept: the tax was charged on the net figure, not on the gross one. This is the single most common percentage error in invoicing, it usually goes unnoticed because the number looks plausible, and an auditor will find it in the first ten minutes.
Why does a 20% rise followed by a 20% fall not bring me back to the start?
Because each percentage is applied to a different base. Start at 100, add 20 per cent and you have 120. Take 20 per cent off 120 and you remove 24, not 20, leaving 96. The rise was calculated on 100 and the fall on 120, so they cannot cancel. The same asymmetry explains why a stock that falls 50 per cent needs to rise 100 per cent to recover, and why a "50 per cent extra free" pack is a 33 per cent discount per unit rather than a 50 per cent one.
What is the difference between margin and markup?
Markup is measured against your cost; margin is measured against your selling price. Buy at 100 and sell at 150 and that is a 50 per cent markup but a 33.3 per cent margin — the same transaction, two different numbers, and mixing them up is how a business prices itself into a loss. If someone quotes you a percentage on a price, ask which base it is on. Use the "what percentage is A of B" mode for margin and the "X% of a number" mode for markup.
Related guides
Percentage Calculations Explained: Online Calculators and Four Sums
Learn the four percentage calculations everyone confuses, with worked examples and formulas so you pick the right base every time.
Sale Maths: Online Calculators for Stacked Discounts and Real Savings
Learn how retailers phrase discounts so you can check the real saving instantly with online calculators and unit-price comparisons.
Unit Prices: Compare Supermarket Costs with Online Calculators
Learn how to compare supermarket unit prices, spot misleading shelf labels, and decide when a bigger pack, multibuy or concentrate saves you money.
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