I found myself in Tesco the other day, doing a shop. I also found myself getting really annoyed.


It was the pricing policy. With a range of items, it can be hard to compare prices, so they 'helpfully' put on the shelf label something like 57p/100g.

Some may object to the SI system being used there. I don't, in fact, I think it's a crying shame that we're stuck halfway between the imperial system with its funny numbers of subunits and the SI system.... but that isn't an argument I want to get into here, it's a distraction from the main point.

Tesco Mustard Pricing

What I objected to was the lack of consistency of which units were chosen for the shelf label - not between different types of item, but between different types of the same class of item. I won't always go for the cheapest item - but if I am paying more it's helpful to be able to fairly compare how much more I'm paying!

Mustard, for example, had prices per kg, prices per 100g (okay, annoying but not too tricky) and prices per 100 millilitre... what? To make a direct conversion I would have to carry around the density of that brand of mustard in my head. I could make an educated guess of about 1gram/millilitre (i.e. asume it's mostly water) - but that could easily be 10% out, making the final price per 100g roughly 10% out - rendering it pointless.

I didn't really care what the basic unit was for price comparison, only that it was the same unit. By mixing units like this the labels are obscuring the information that they're trying to make clear.

I thought that what's happened is they've got some bit of software doing this which says 'If it's over X pence per 100g, give the price as pound sterling per kg' and the same bit of software chooses whether volume of mass is the appropriate unit (kg is a unit of mass, not weight, there is a difference - imperial doesn't make the distinction). Why on earth can't they make their pricing software say 'It's mustard. Look at the results of the other mustard calculations, and if the majority are prices per 100g, then we'll force that for all mustard and flag up any lines where the mass is unknown for referral to the supplier'.

Actually, it's not even that - as some of the pricier mustards are per kg. What is going on?

It is not an excuse to say 'some jars are labelled in millilitres, and some in grams therefore it's all we can do'. Tesco have enough clout to be able to say to their suppliers 'give us this data if you want us to stock your product' - and this certainly wouldn't explain the 100g vs kg inconsistency (which is annoying but not insurmountable by the customer).

The only reasons I can think of for the status quo and for this bit of logic being missing are:

  1. Genuine oversight.
  2. Deliberate obfuscation, whilst trying to appear helpful (i.e. making more expensive products as price per 100g or price per 10g, whilst making cheaper products price per kg)
  3. Incompetence.

Whichever is the truth, the lack of consistency within product lines got really annoying, and I decided to fill out a comment form. At the front of the store was the 'customer feedback' display board, which contained the usual selected quotes asking for things they'd implemented years ago, with the smug 'reply' underneath. No forms were to be seen...

I went to 'customer service' for a form, waited to be served, and then had to wait for them to hunt for a form for me. I didn't get the impression that they got asked for these often. Hint to Tesco: If you really want customer feedback, make the forms really obvious - don't hide them away.

I've requested a reply. Let's see what they say. I hope they sort it out; every little improvement would help...!

As an aside: Interestingly, the kilogram is the only base unit with 'kilo' in front of its name. I wonder how that happened?