/ Food & Drink, Health, Shopping

Food labels – do we need calories and kilojoules?

A food label showing calories

Most of us know how to work with calories. I know I can consume around 2,000 kcal a day as a woman, and that men are recommended 2,500 on average. So will a law to add kilojoules to packaging confuse shoppers?

For years now, we’ve gotten used to seeing the energy content of food shown in calories (kcals), and most of us understand the concept. Recipes give energy information in calories, ready meals state how many calories they contain and, more recently, a number of restaurants have started to display the calorie content of their meals.

Simpler food labels

At Which?, we’ve been campaigning for simple food labelling that gives people the information they need to help them make healthy choices. Currently, most front-of-pack labelling gives the energy content of the food in calories and the sugar, fat, saturated fat and salt in grams.

This is great news for shoppers – especially as all the major retailers have now committed to traffic light labelling as well. This means that people will finally be able to tell at a glance whether the food they’re choosing is high, medium or low in various nutrients.

However, new EU legislation will now make it compulsory for food manufacturers to label the energy content of foods in kilojoules (kJ) as well as calories. At the moment, kJ are already provided on the back-of-pack labelling. But under the new rules, if there is a front of pack label, then the energy content will have to be displayed both front and back. Those that fail to do so will be breaking the law.

Over-packing the packaging

Although kJ may be the correct scientific way to represent energy, I question how useful it will be to people. After all, how many of us really know how many kJ we should consume a day, or how many kJ are in a kcal? When we asked over 2,000 people in an online poll last August, 61%  wanted to see kcal displayed on food labels by itself. An additional 22% wanted kcal and kJ displayed together, but only 1% wanted kJ alone.

Many food manufacturers have said they’re concerned that this extra information on the front of food packages may confuse people, as well as overcrowding the packaging. Obviously, in this matter, the manufacturers’ hands are tied.

As the legislation has passed, we will soon have to get used to seeing both kJ and kcals on food packaging. But even so, I think I’ll stick to using the kcals to make a quick and informed decision about whether to buy or not. Do you use kcals, kilojoules or both when choosing your food? Do you think the extra info will crowd the packaging, or provide useful information?

What information would you like to see on food packaging?

Calories (kcals) (62%, 190 Votes)

Both calories and kilojoules (28%, 86 Votes)

Kilojoules (kJ) (10%, 29 Votes)

Total Voters: 309

Loading ... Loading ...

If the quest to use SI units were serious then we’d be buying electricity in kJ instead of kWh. The key thing here is meaningfulness. Calories, despite their quirky definition, are understood in popular culture. There’s no instance of Joules being understood in popular culture. Why throw away one of the few measurement units that people seem to be able to understand?

“There’s no instance of Joules being understood in popular culture”.

Well, that’s a problem, and that (if true) is a good reason to change. Our youngsters need to understand Joules along with the rest of the weights and measures system or we’ll never be able to generate sufficient scientists and engineers to drive our nation up in the world rankings and out of this recession.

I think you need to learn the difference between joule and watt hour…

Martin F says:
24 February 2013

We need to move to kJ and forget about Calories, an old and outdated way of trying to measure energy, from some weird equipment used to measure bombs in the early 1900s. Look up Atwater system: Totally inadequate for our modern dietary needs.


Malc.Moore says:
24 February 2013

New York State Claim using Calories is starting to change American Attitudes to-wards eating; even the Big Burger firms are supporting the introduction of how many Calories in their menu; which is a surprise there is talk that it is to go Countrywide. kilojoules will be rejected by the British Public if this happens most Ethnic British whites regard America as Britain’s Allie much more than the E.U.

“most Ethnic British whites regard America as Britain’s Allie (sic) much more than the E.U. ”

Sorry – what’s the E.U. got to do with the fact that the Joule is the S.I. unit of energy?

Do we need calories and kilojoules?
Do we need calories or kilojoules?
My thoughts on this matter is very clear, and its probably contrary to the thoughts of the good people at Which?
Food labels (nutritional labels) should have the word “Energy” on them, and the value of the energy should be in kilojoules (kJ) only.
1… The unit calorie is a metric unit, but from the older centimetre-gram-second (cgs) era of metric development. It is not a modern metric (SI) unit.
2… The UK is officially metric. It uses the modern metric system (SI). That is the standard that has been set (ie SI). Any metric labelling should be SI.
3… The SI unit for energy is the joule (kilojoule).
4… It’s always important to get it right first time. Regardless of the popularity of the older calorie unit, the joule (or kilojoule) is the correct unit.
5… Food labelling especially nutritional labelling, is not a popularity contest. It’s very important for the nations health that information on the labels use the correct units. 
Thanks for the opportunity to comment..

The joule (kilojoule) and the calorie (kilocalorie) are now starting to appear on supermarket and shop shelves.

The following link connects to an article by UKMA.


This is being driven by a new EU requirement to show both kJ and kcal. Hopefully the next step will be to get rid of kcal.

Malc.Moore says:
10 May 2013

When i read a food product information 1st i look for salt content then fat.I was horrified in Ready meals the salt content is so high i dropped the Ready meal like a hot piece of metal.I cannot understand why a can of baked beans with lower sugar&salt costs more than an ordinary can of beans surely they should be less or the same?.

It costs as much as they can get you to pay for it, that’s called capitalism. Though they probably loss lead ordinary beans a bit if they are likely to end up something like a Which? comparison shopping basket or if the industry has got one of its “1000 cheapest items” price war going on.

The UK and the US are only partially metricated, and have confused nutritional labels on packaged foods, whereas Australia that has metricated, (although not totally metric), and has clear SI units on nutritional labels.

The US has similar nutritional labeling problems to the UK, whereas Australia have no problem.

Australia has set the example that the UK and US should follow.

The following is an article from US blogger The Metric Maven it has a picture of the clear SI labeling used in Australia.


As a subscriber to “Which?” magazine, I am disappointed to learn from that article at the UKMA’s site, that the Consumers’ Association apparently lobbied the goverment to try and keep the confusing status quo mess involving kCal.

And at the expense of kJ too. What were you thinking, you guys??

It seems fairly obvious to me reading here that no-one has an issue with kJ being involved, the question seems to me mostly whether you want “just kJ” or “kJ plus kCal”.

So what the hell were the CA doing lobbying for just kCal (and getting *all* the abbreviations for just about all the units wrong too!).

The problem is that the vast majority of people are familiar with ‘calories’. I think this should always be written as Calories or kcal to distinguish them from the calorie that a scientist would use. Incidentally, it’s kcal and not kCal.

It seems logical to label food with kJ and kcal to help the public make the transition to kJ only. Prior to decimalisation in 1971, prices were shown in the new and old system for at least a year and the old £sd gradually disappeared after the changes had been introduced. This change was helped through by the fact that we had to use the new currency.

When we have labelling in kJ and kcal, those writing cookery books and recipes should get on and support the move to kJ. I am not optimistic because many writers stuck with Fahrenheit and I think it was that the oven manufacturers that helped us to move to from Fahrenheit to centigrade.

Asda now shows energy values in kilojoules (kJ) on the front of products, for example ‘Mexican Chilli Chicken’.

Daniel Clad says:
1 November 2013

1 kilojoule = 239.005736 calories. You can visit online tools to calculate kilojoules to calories

The whole concept is flawed says:
30 June 2015

The whole concept is flawed as food manufacturers and labelers have absolutely no idea of energy units. They just put what looks or sounds good.

I am a man so on average I need between 2200-2500 calories to survive. This translates to 2.2-2.5 Kcal. Let’s go with the lower figure for the moment but any one would do.
I need 2.2 Kcal. I bought a packet of ‘3 minute’ noodles which has 492 Kcal per 100 gm. The packet is 60 gm so the actual energy content of the packet is 60% of 492 = 295.2 Kcal.

Weheyyyyyyyy :)) This small 60 gram packet of ‘3minute’ noodles will last me for 134 days supplying the full amount of energy that my body needs for this period.

This labelling is not just on these noodles but on ALL products.

Before anyone has a go, let’s clarify somethinf. I am a physics graduate with a Master’s degree in Thermal Energy so I work with Joules, Calories, BTU, and their Kilo counterparts on a daily basis.

The labelling should remove the Kcal and just call it cal if that is what is meant.

Nutrition labels – who checks the quality of information provided?

Compare two bottles of distilled malt vinegar:
Same product – one with an energy value 3 times the energy value of the other.
ASDA (bar code: 2100 6296) 586 ml bottle
Energy 26 kJ per 100 ml
SAINSBURY’S (bar code: 0189 3212) 586 ml bottle
Energy 77 kJ per 100 ml
It says the ASDA is produced in Spain. For the Sainsbury’s one it’s produced in the UK.

Are Local Authority Trading Standards Officers responsible for checking the accuracy of the values stated on the nutrition labels?

Is it possible for one type of distilled malt vinegar to have an energy value about three times greater than another sample?

The values for Fat, Carbohydrate, Fibre, Protein, etc. are very similar.
These values (in grams) are shown below:
Fat 0 [ASDA] < 0.5 [SAINSBURY’S]
Carbohydrates 1.0 [ASDA] < 0.5 [SAINSBURY’S]
Fibre 0 [ASDA] < 0.5 [SAINSBURY’S]
Protein < 0.5 [ASDA] < 0.5 [SAINSBURY’S]
Salt 0 [ASDA] < 0.01 [SAINSBURY’S]

For the Sainsbury’s product it also provides the values per tablespoon (15 ml), these are given below:
Energy 12 kJ, then in the same order Fat, Carbohydrate, etc
< 0.5; < 0.5; < 0.5; < 0.5; < 0.5;

I’m glad I’m not the only one who compares the nutritional information of products and wonders why similar products differ so much. Unlike the ‘non-brewed condiment’ used in fish & chip shops, proper vinegar is fermented and could contain different amounts of acetic acid, protein and carbohydrate. As explained on Wikipedia, the description ‘distilled malt vinegar’ is a misrepresentation, since vinegar is not distilled.

Trading Standards seem to devote their time on major issues such as dangerous counterfeit goods being imported in bulk, and I very much doubt that they would be interested in dodgy nutrition labels.

It seems the food industry uses kcals and cals interchangeably. Rather strange. I’ve wondered about that for a long time.

The easy way to avoid the confusion is to use Cal to represent kcal, or better to use kJ so there is no possibility of confusion.