Discount Calculator

The basic calculation

A discount is simply a percentage of the original price, subtracted from it. An £80 item at 25% off loses £20 (25% of £80) and costs £60. The same arithmetic runs the other way too: if you know the sale price and the original price, the discount is the saving divided by the original price, so a £60 sale price on an £80 item is a 25% discount. Our percentage calculator covers that reverse direction if you need it.

Where shoppers get caught out is the reference price. A discount is only as good as the price it is taken from: a retailer that raises a price before a sale can advertise a large percentage off a price the item rarely sold at. Always compare the sale price with what the item usually costs elsewhere, not with the struck-through figure on the tag.

Why stacked discounts do not add up

Sale events love a second code: 25% off, plus an extra 10% off at checkout. It is tempting to call that 35% off, but the second discount applies to the already-reduced price, not the original. On £80: 25% off leaves £60, then 10% off £60 removes £6, leaving £54 — a total saving of £26, or 32.5% off, not 35%. The gap widens as the percentages grow: 50% off plus 50% off is 75% off, not free.

The calculator handles this by applying each discount in sequence, and it reports the effective discount so you can compare stacked offers honestly against a single larger discount. A straight 30% off beats 20% plus 10% (28% effective), and a single 40% off beats 25% plus 20% (40% versus 40% — a tie, in that case).

Discounts, VAT and the price you actually pay

In the UK, consumer prices are normally shown including VAT, so the discounted shelf price is the price you pay — the calculator's result needs no further adjustment. The exception is business-to-business or trade pricing, where prices may be quoted excluding VAT: a 20% discount on an ex-VAT price still leaves 20% VAT to add at checkout, which changes the final figure by a fifth.

The same caution applies to delivery and fees, which are rarely discounted. A 30% saving on the item can shrink quickly once a delivery charge is added, and some retailers exclude sale items from free-delivery thresholds. Judge the deal on the total at checkout, not on the percentage in the headline.