How to compare supermarket unit prices
Unit prices are the fairest way to compare products of different sizes. Here is how to use them.
5 April 2026 · 1 min read
What is a unit price?
A unit price shows how much a product costs per 100g, per litre, or per unit — making it possible to compare products of different sizes fairly. UK supermarkets are legally required to display unit prices on shelf labels. Looking at the unit price rather than the headline pack price is the most reliable way to work out which option actually represents better value.
Bigger is not always cheaper
A larger pack often has a lower unit price, but not always. Promotional pricing, loyalty card offers and own-brand alternatives can all shift which option is cheapest on a given day. It is worth checking the unit price even when something looks obviously like a bulk bargain, as the saving is sometimes smaller than it appears.
Using unit prices across retailers
Keeping a rough note of unit prices for items you buy regularly helps you recognise a genuine deal when you see one. Some shoppers keep a simple list on their phone with unit prices for household staples, which makes comparing across stores quick and practical. Even a rough mental benchmark is enough to spot when a promoted price is not as competitive as it looks.
General guidance only
This guide contains general consumer information and is not financial, legal or professional advice. Always check official sources and consult a qualified professional if you need guidance specific to your situation.