/ Food & Drink, Shopping

Is your food lighter than it claims?

Tin with tape measure

Are the grams on the supermarket products you buy accurate? Our snapshot investigation of 467 supermarket products found that some weighed significantly less…

In 2012 we discovered that 80% of the smoked salmon packs we’d measured were underweight. We wanted to broaden our test for 2015, so we asked food fraud expert Professor Chris Elliot to help us investigate underweight food in supermarkets.

His researchers at Queen’s University Belfast weighed 467 food products bought from supermarkets in Northern Ireland and found that 73 were below the recognised margin of error (this ranges from 4.5g on a product weighing 50g or 15g for a 1kg product).

Products that we found weighed less

Products weighing less than the margin of error:

  • 23 out of 32 tins of Heinz Chunky Veg Big Soup.
  • Six out of eight samples of Tesco Finest smoked salmon.
  • 19 out of 31 Green Giant Niblets Original Sweetcorn contained less than the drained weight stated on packaging.
  • Four out of 32 Del Monte Peach Slices in light syrup. Two were very underweight.
underweight foods

We’d expect a small variation in weight, which the margin of error accounts for, but we were surprised by how many samples were below this.

Enforcement for underweight foods

Trading standards officer Paul Ferris couldn’t comment on our research as it wasn’t carried out by accredited weights and measures professionals, but he did say:

‘Discrepancies may be due to natural desiccation of the product – as stated weight relates to the time of packing – inadequate staff training on packing, or incorrectly using weighing equipment.’

It’s important that manufacturers have effective checks in place to make sure you aren’t getting short-changed. And if products are found to be underweight, it’s important that Trading Standards continues its enforcement to help ensure compliance.

What do you think about underweight food? Are you sometimes suspicious that a product is lighter than it claims? Do you ever go to the lengths of getting the scales out to prove a point?


An excellent exposé.

The Tesco Finest smoked salmon is a premium product and priced accordingly at £4.80 per 100 gm. If the margin of error is 9 gm on a 100 gm pack and 75% of the product in the sample is short of even that benchmark that is a serious contravention, or “diddling” to use the technical term for it. I hope that an accredited professional trading standards officer using the correct and certified apparatus will immediately carry out some evidence-quality tests and take enforcement action if the Queen’s University results are sustained. Should look beyond Tesco as well – it could be widespread.

As for tinned produce, that is more perplexing because I should be most surprised if companies like Heinz, Green Giant and Del Monte did not have weighing equipment in their canning lines [but it has to be calibrated and tested correctly, of course, which requires technical competence]. There is the possibility – but unlikely in my view across three separate manufacturers – that the production lines were adjusted to reduce the weight of the contents [while keeping the price the same?] but nobody corrected the pack weight on the can label. I wonder how full the cans were – with small element product like soup and sweetcorn it should be easy to make sure they are all filled up to the declared weight. With the peaches some extra syrup would bring the weight up if another slice could not be squeezed in, but over 6% of the sample were very underweight – two or more slices short of a full tin perhaps. Since the production and packing processes are probably almost entirely automatic there must be some particular explanation for this and I think we should be told.

And yes, I do often use the weighing scales in supermarkets to check the weights of packed products, but it never occurred to me that the canned fruit, soups and vegetables would be deficient. I suppose it doesn’t occur to Tesco, Sainsbury, Asda, et al, to do routine check-weighing of their bought-in products as well since they are being ripped off by the manufacturers and will have insult added to injury when they have to stand up in court. Selling short weight has historically been a very reprehensible offence.

Apart from the obvious short-changing effect of unreliable product weights for shoppers, it distorts the unit pricing comparisons and value for money calculations that the industry and consumer bodies depend upon.


I wonder what will happen as a result of these companies being found to be breaking the law. Will they just be informed of the problem, or will legal action be taken? A typical response to criticism to investigation of problems of this nature seems to be a prompt and polite response stating that as a reputable company we take the matter seriously and will carry out a detailed investigation. Will anything happen or will it be business as usual once the public has forgotten the news story?

I hope we will find that the short measures are as a result of carelessness and failure to maintaning machinery rather than a deliberate attempt to cheat the public.

Please can Prof Elliott have his second ‘t’.


So even Which? short changes us by giving Chris Elliott fewer letters. ;_D

I find it a cop-out that Trading Standards would not comment because Queens were “not accredited”. Are they incapable of accurately measuring 467 products ? Are tinned products losing weight by dessication? Or are they just reluctant to get involved?

These products are from major manufacturers with the technology and quality control to give the amount of product they wish. What would be useful to know is what proportion of the various products were overweight. That would tell us whether their controls are genuinely defective or whether it all works in their favour. Perhaps Prof. Elliott could tell us.

I would like to see the product weight or volume stated being the “minimum”, not subject to a minus tolerance. Then, without having to dig out the regulations, I will know if I am being short-changed. I should get what I pay for.


I agree that giving a minimum weight would be useful. That would encourage us to go to Trading Standards if we are short-changed. I believe that it is illegal for a barman to give you more alcohol than we pay for but I am not aware of other examples.

We still use the term ‘baker’s dozen’, dating from a time when bakers used to give thirteen items when we ordered twelve. Going back to our history books may be the way forward.


I was told that bakers added such things as chalk so they managed to make 13 loaves from the flour for 12. I don’t think we ever left that era.


wavechange, you are in danger of opening old wounds with you bakers dozen – remember the “Is now the time to ditch imperial and go fully metric?” conversation? The quantity should now perhaps be 11.


Selling in quantities of ten makes it easy to work out the price of a single item. Eggs are often sold in packs of ten.

It would help the consumer if products such as the ones illustrated in Shefalee’s introduction were sold in a multiple of 100g. So full marks for the 400g can of Heinz soup but not for the 285g of sweetcorn or 420g of peach slices. It would make sense to move to 300g of sweetcorn and 400g of peach slices. If these were minimum weights, so much the better.


Excellent idea, but perhaps can-size standardisation has something to do with it and the relative densities of different products. As I said earlier, the deficiency tolerance [and breaches of it] make a mockery of the unit pricing system.


Of course you are right about the nature of the product, John, and it would not make sense to sell English mustard in 400g quantities, like canned soup. For mustard, perhaps 50g and 100g jars would be useful preferred sizes.

With some products such as instant coffee, the common sizes are 100g, 200g and 300g irrespective of manufacturer. A confirmed tea drinker might have a 50g jar for the benefit of visitors, but most buyers buy the sizes I mentioned.

For milk, I suggest 0.5, 1 and 2 litres. It’s time to get rid of strange quantities such as 1.135 litres and 2.27 litres.


I go along with that. A modular system would make life simpler. As happens already with some tinned fruit, cans could have the same circumference but be shorter or taller according to the contents and preferred quantities but all be graduated to sensible common units [multiples of 50g]. It’s interesting that when we had cats we noticed that all the cat food tins were the same size but the weights differed quite considerably across different brands making value comparisons tricky [this was before unit pricing was common on shelf edge labels], so accommodating different densities can be done. With goods in other packaging the restrictions of standardised cylindrical cans do not apply: every manufacturer [and brand] can still have their own distinctive shape in glass or plastic but still follow the modular weight/volume/quantity standard. If you look at washing-up liquids at the moment, the variety of contents volumes across the brands is quite bizarre and the actual amounts seem to make no sense at all – I suspect it’s all done to confuse us over special offers which always seem to come in unique and unrelated quantities. Perhaps it would be argued that the concentration rates for different products packed on the same production lines in identically shaped containers have something to do with it but I see little evidence of that in practice. And I hardly dare mention toothpaste tubes which are almost beyond comparison by virtue of the haphazard sizing [and then they’re boxed in such a way that makes it even more difficult to judge visually]. Unit pricing is the shopper’s safety net but, as we know from other Conversations on the relationship between price and pack-size, errors are commonplace because of the complexity. And putting less product in the same size container for the same price has become an important element of the retailers’ black arts [not forgetting that an identical container in a pound shop will not necessarily contain the same quantity as the same product in a different store, which I am sure fools many customers]. On milk, I think I am correct in saying that the smallest bottles are basically still pints but marked with their metric equivalents!


I expect we will have to carry on wishing for preferred sizes of cans and jars, because any attempt to decrease the amount we were buying would not go unnoticed. We might be better to push for minimum weights, as suggested by Malcolm. When goods are weighed out for the customer, the amount is never underweight and sometimes rather generous.

I was pretending not to understand the strange quantities that milk is often sold in, though I don’t pretend to understand why this is still going on in 2015. Bottled beer generally comes in 0.5 litre measures these days and pubs in the north often supply a generous 0.5 litres in quaint glasses marked ‘Pint’.

Perhaps if we all turn up at the supermarket with an electronic kitchen scale and start weighing the packets as we progress round the store. Even though we cannot measure the weight of the contents of a package, the gross weight will let us select the ones that offer the best value for money and the some others that might interest Trading Standards.


You do need to keep an eye on the till operator if they weigh products to price them at the checkout. They don’t always take their hands off the product so it could cost you more.

I remember when you had to weigh and price up your fruit and veg before you got to the till. One machine had a queue of people waiting at it while the other was free. The reason? The word soon got round that one weighed less than the other !!!