/ Food & Drink

Why’s it so hard to work out the cost of a banana?

Illustration asking how much for a banana?

Seven mini bananas will cost you 99p for the bunch (or 14.1p each). Loose bananas cost 68p per kg. From this information, can you work out what’s cheapest to buy? Welcome to world of confusing supermarket unit pricing.

With a busy job and excitable children, a visit to the supermarket needs to be a simple and speedy affair.

I don’t have the time to pore over supermarket shelves to work out the best price for my purchases.

Unit pricing is a great idea in theory. It’s a useful tool for people to compare food prices and choose the best value product.

But our research shows unclear and inconsistent use of unit prices in supermarkets is preventing cash-strapped consumers from being able to work out which products are cheapest.

Supermarket sweep

We sent our supermarket shoppers on a mission to visit all the major supermarkets at a number of locations across the UK to see the extent of the problem.

Their research highlighted some interesting issues – for a start, unit pricing was sometimes being used by referencing the quantity and sometimes the weight. What’s more, they were often not being shown for multi-buys or promotions and some pricing was too small to read – or non-existent.

Along with the banana example we found red peppers in 500g packs on sale for £2.09 or £4.18 per kg next to packs of three mixed peppers priced at £1.65 or 56p each. Confused? Don’t worry, so am I. These are just a couple of examples we found – see more in our gallery (for further information about each image, visit our Flickr page):


Clear, consistent food pricing

Which? wants clear, consistent food pricing where the unit price is prominent and easy to read. We also want consistency in the units used on all products and for multi-buys and promotions to show the unit price.

Is unit pricing a bugbear of yours? We’re going to up the pressure on government and retailers in the coming months to simplify unit pricing for you.

If you feel strongly about the issue we’d love your views or examples of confusing unit pricing. If you’ve caught the issues on camera, tweet us your photo or email it to which.campaigns@which.co.uk. We’ll add the best of the bunch to our online gallery.

Andy Frame says:
11 July 2012

In my local coop: 400g Hellmans Mayonnaise £1.99 or 750ml squeezy bottle of the same stuff £2.09. How on earth can you tell which is the best value for money?

Michael says:
12 July 2012

I hate this inconsistent use of units on products. To my mind if something isn’t solid it should be sold by volume ie Litres, and if it’s solid it should be sold by weight/mass ie Grammes. However, the beauty of the metric system is that volume and weight are interlinked. 1 Litre of water weighs 1 kilogram – a definition at the very heart of the system. So in this instance the jar of mayo at 400g ie 0.4 kg sounds poorer value than the 0.75L of squeezy mayo. There should have been some unit price indicators to make this comparison easier but retailers have a habit of 1) mixing volume and mass as in this example – a simple, statutory rule is needed here regarding when to use grammes or litres. 2) retailers also vary the basis of their unit price to suit themselves. Eg some items are Priced per Kg and some per 100g. Now I know it’s only case of moving the decimal point to the left or right, but it’s still done to confuse isn’t it!

Phil says:
16 July 2012

“a simple, statutory rule is needed here regarding when to use grammes or litres” – there is legislation in place that dictates what mom (units of measure) should be used for each food type.
Whilst I agree that certain supermarket chains are abusing confusion over unit pricing to their advantage, it must be pointed out that most of the blame for the unit pricing fiasco is down to the original legislation. I was working for a food retailer when it was introduced and I recall that most large retailers at the time said it was flawed and would lead to confusion, which unfortunately has proved to be the case. The first step in putting this right has to be to simplify the unit prices legislation. Then its will be simpler to tackle those supermarkets who are abusing it.


Yes, a litre of water weighs a kilogram. But that is only true of water. For other substances (e.g vegetable oil) the conversion will differ as it relates the the density of the substance.