Why the cheaper pack can cost you more
A smaller pack, or one on offer, costs less at the till. Work out what you pay for each kg and it can cost more than the bigger pack next to it.
- On offer Cheddar, 200g £2.40 £12.00 a kg
- Usual price Cheddar, 400g £3.60 £9.00 a kg Better value
You don’t have to do the sums. Big supermarkets show the price per kg on the shelf label. The government’s guidance says what it’s for: “It allows consumers to compare the price and value of similar products.” (Department for Business and Trade)
Check multibuys the same way. Three for £5 is a deal only if the price per kg is at the good end of the price guide.
A price guide for everything on your list
Every line on your Nomstash shopping list has a price guide per kg, from a good price to a dear one, without you typing anything in. It starts in the unit the shelf label uses, and you can switch to per 100g or each.
No time to check every line? Start with the dearest things on your list, such as the meat and the cheese.
- At the good end of the guide A good price. Put it in the basket.
- At the dear end Look along the shelf. The bigger pack or the own brand may cost less per kg.
Shopping online? The same rules cover online shops, so look for the price per kg there too.
A bigger pack only pays if you use it all
When the bigger pack is the better price per kg, it’s only good value if none of it goes in the bin. On a cook day, three dishes come from one shopping list, so the big bag of onions goes into all three before it goes soft.
For the bits that are left over, use the whole bag has a recipe for the peelings, the stalks and the end of the loaf.
What the price guide is
A guide to what’s normal, so you can tell a fair price from a dear one. It isn’t the price at your shop today, and it doesn’t say which shop is cheapest.
Our prices are estimates, not quotes. We regularly check what a broad cross section of everyday products, at different prices, cost across several major UK supermarkets, and use a typical price from the middle of what we find.
What you pay depends on where you shop, what you pick and the offers on the day.
More on how we estimate prices, and every other claim we make, is on our claims page.
Sources
- Department for Business and Trade The Price Marking Order 2004: government guidance (Sept 2025) gov.uk
Last checked . Each quotation on this page was read against the page it links to.