Discount calculator

Every answer above shows its working, so you can check it or do the same sum at the till. These are the rules I follow.

A percentage off

Work out the percentage of the price, then take it off. When the saving lands on part of a penny I round to the nearest penny, half a penny up. Shops round too, some on each item and some on the whole basket, so the checkout can come out a penny either side.

A sale and a code together

A second discount comes off the price the first one left, never the original, so two discounts always come to less than their total. That matters when a code says it works on sale items: 30% off a price already cut by 40% takes 58% off in all, not 70%.

Multi-buys

A 3 for 2 or buy one get one free only counts whole groups: buy five on a 3 for 2 and one is free, not one and two-thirds. I flag when an offer needs one more item, or more spend, to kick in, and when a "3 for £10" costs more than buying the items on their own.

Price per kilo, litre or item

Since 6 April 2026, when the latest changes to the Price Marking Order took effect, unit prices in Great Britain have been per kilogram or litre, or per item for things sold by number, in shops and online. That's why I compare packs on the same units, so the answer matches the label you're standing in front of. Shops of up to 280 square metres don't have to show unit prices on goods packed in fixed amounts.

For codes that work at a particular shop, each store page lists the ones I've checked. To see whether a price is really low, the price drops page tracks the products I watch.