Discount Calculator
Work out the discounted price and savings. You can calculate by entering a discount percentage, or by entering the final sale price to find the discount percentage.
How the Discount Calculator works
This calculator works in two modes. If you know the discount percentage, enter the original price and the discount to see the sale price and how much you save. If you already know the final price, enter the original and final prices and the calculator will work out the discount percentage for you — useful for checking whether a sale is as good as it looks.
An optional VAT field lets you calculate the VAT-inclusive price on the discounted amount. In the UK, most consumer goods include VAT at 20% already, but for business purchases where VAT is quoted separately, this can be helpful for understanding the full cost after discount.
When evaluating sale prices in UK shops, it is worth noting that retailers must show a genuine previous selling price for any sale claim. If a product is advertised as "was £100, now £75", the £100 price must have been charged for a meaningful period. This rule is enforced by the Competition and Markets Authority under the Unfair Commercial Practices Directive.
Frequently asked questions
How do I calculate a discount?
To calculate a discount, multiply the original price by the discount percentage divided by 100. For example, a 25% discount on a £80 item is £80 × 0.25 = £20 saving, giving a sale price of £60. Alternatively, multiply the original price by (1 minus the decimal discount): £80 × 0.75 = £60.
What is the difference between a percentage discount and a pound-off discount?
A percentage discount reduces the price by a proportion of the original — so a 20% discount saves more in absolute terms on expensive items than cheap ones. A pound-off discount (such as £5 off) gives a fixed saving regardless of the original price. Percentage discounts tend to be more attractive on higher-priced goods, while pound-off promotions can represent excellent value on lower-priced items.
How do stacked discounts work?
Stacked discounts apply multiple reductions in sequence rather than adding them together. For example, a 20% discount followed by a further 10% discount does not equal 30% off. Instead, you pay 80% of the original price, then 90% of that: 0.80 × 0.90 = 0.72, meaning you pay 72% of the original price — a 28% total saving, not 30%. Always apply each discount to the running price, not the original.
Is 50% off better than buy-one-get-one-free?
They are mathematically equivalent when comparing two identical units: both result in paying for one item and getting one free, so the effective cost per unit is the same. However, buy-one-get-one-free requires you to take two units, which only represents value if you will actually use both. If you only need one item, a genuine 50% discount is more useful as you pay half price for the single item you want.