Kilojoules to Kilocalories on EU and UK Food Labels

Two Energy Numbers on the Back of Every European Pack

Turn a packet over anywhere in the EU or the UK and the nutrition table opens with two energy figures rather than one: kilojoules first, kilocalories immediately after. Australia and New Zealand go further and print kilojoules alone. If you grew up counting kilocalories, the leading number is the larger and less familiar one, and the habit that helps most in the aisle is knowing roughly what it means before you get to the second column.

Conversion factor: 1 kJ = 0.239 kcal, and 1 kcal = 4.184 kJ — the same factor European food-labelling law uses. A breakfast cereal at 1 600 kJ per 100 g works out at 1 600 × 0.239 = 382 kcal per 100 g, which is what the second column on that pack will say.

What the Label Is Obliged to Tell You

Regulation 1169/2011 Sets the Order

EU food information rules require energy to be declared per 100 g or per 100 ml in both kilojoules and kilocalories, in that sequence, before any of the nutrient rows. The UK kept the same requirement, which is why a British pack still leads with a kilojoule figure most shoppers never read.

Australia and New Zealand Print kJ Only

Under the Australia New Zealand Food Standards Code, energy is declared in kilojoules and the kilocalorie column is optional — most manufacturers leave it off. A pack bought in Sydney gives you one number, and converting it is the only way to compare it with a recipe or app that thinks in kilocalories.

The Reference Intake Is a Fixed Average

Every percentage on a European front-of-pack is measured against 8 400 kJ / 2 000 kcal a day. It is a labelling constant for an average adult, not advice for you specifically, and it is why identical products carry identical percentages regardless of who picks them up.

4.184 Is Written Into the Law

The conversion is not a manufacturer's choice. The same annex that lists 17 kJ/g for carbohydrate and 37 kJ/g for fat fixes the kilojoule-to-kilocalorie relationship, so the two energy columns on a compliant pack are arithmetically tied to one another.

Reading a Pack in the Aisle Without Doing the Arithmetic

Most comparisons in a supermarket come down to putting two packs on the same scale. The quickest route is to work from the per-100 g row, which every label must carry, rather than the per-serving column, which each brand defines for itself.

Take the kilojoule figure from the per-100 g row

Ignore the serving column while comparing products — one cereal calls 30 g a portion and another calls it 45 g. The per-100 g row is standardised across every pack in the shop, which makes it the only column where two products can be judged fairly against each other.

Type it in and read the kilocalorie value beside it

The second field fills in while you type, so a four-digit kilojoule figure becomes a familiar kilocalorie number without pressing anything. Continental labels that write a decimal with a comma are read correctly, and spaces used to group thousands are ignored on the way in.

Reverse it when a recipe is the thing in kilocalories

Cookbooks, restaurant menus and most fitness apps still quote kilocalories, so the comparison often runs the other way. The swap arrows turn the pair round, and either side accepts input, so a menu figure can be put next to a kilojoule-only pack in one step.

Copy the number into your shopping note or tracker

The copy control above each field gives the digits with no unit attached, ready to drop into a notes app, a spreadsheet of weekly shopping, or a food diary that only accepts plain numbers in its energy box.

Per 100 g is not per pack: a bag of crisps at 521 kcal per 100 g contains about 156 kcal if the bag holds 30 g. Multiply by the actual weight before comparing a snack with a meal, or the per-100 g figure will make everything dry and concentrated look alarming and everything watery look virtuous.

Packaged Foods per 100 Grams in Kilojoules and Kilocalories

These are representative back-of-pack figures across the range you meet in a weekly shop, from a watery product to pure fat, with the share of the 8 400 kJ daily reference intake that 100 g would use up.

Food, per 100 g or 100 ml	Energy (kJ)	Energy (kcal)	% of 8 400 kJ reference intake
Skimmed milk	146	35	1.7 %
Plain low-fat yoghurt	251	60	3.0 %
Cooked pasta	620	148	7.4 %
Wholemeal bread	985	235	11.7 %
Cornflakes	1 600	382	19.0 %
Cheddar cheese	1 725	412	20.5 %
Potato crisps	2 180	521	26.0 %
Milk chocolate	2 240	535	26.7 %
Olive oil	3 700	884	44.0 %

Water is what really separates the top of the table from the bottom: skimmed milk is mostly water and olive oil contains none, which alone accounts for a twenty-five-fold difference. Note too that many oil bottles print 3 700 kJ beside a rounded 900 kcal even though the arithmetic gives 884 — rounding rules allow it, and it is a reminder that the two columns need not agree to the last digit.

What Helps When the Pack Is in Your Hand

One Pack After Another Without Clearing

Comparing four cereals means four kilojoule figures in quick succession. Type each one over the last and the kilocalorie value follows immediately, so a shelf can be worked through in the time it takes to pick the boxes up.

The kcal Digits Alone for a Shopping Note

Copying returns the bare number with nothing appended, which suits a diary entry or a note listing what you actually bought. There is no unit text to delete before the figure will sit in a numeric column.

Continental Labels Written With a Comma

French, German and Spanish packs write 1 046,5 where a British one writes 1,046.5. Both forms are understood on entry, so a figure read off a pack bought abroad does not have to be rewritten before it converts.

Reading a kJ-Only Pack From Either Side

An Australian label gives you nothing but kilojoules, while a recipe gives you nothing but kilocalories. Because both fields accept input and drive the other, the comparison works from whichever end you happen to have a number for.

Label Questions From the Supermarket Aisle

Why does the pack print two energy numbers instead of one?

Because the law asks for the scientific unit and the familiar one together. The kilojoule is the SI unit and the one EU rules put first, but a century of dietary advice was written in kilocalories and shoppers still think in them. Rather than force a change of habit, the regulation requires both, which is why the leading figure on a European pack is the one almost nobody uses.

What does the 8 400 kJ reference intake mean for the percentage on the front?

It is the denominator, and nothing more. A portion showing 15 % supplies 15 % of 8 400 kJ, or about 1 260 kJ. The figure represents an average adult and takes no account of size, age or activity, so someone with a genuine daily need of 10 500 kJ is reading percentages that overstate every product by a quarter. Treat it as a way of ranking packs against each other, not as a personal budget.

Why does an Australian pack have no kilocalorie figure at all?

Australia and New Zealand adopted metric energy units for food outright, so the Food Standards Code requires kilojoules and treats kilocalories as optional extra information. Public health messaging followed — the well-known 8 700 kJ average adult intake used in Australian campaigns is quoted in kilojoules, never converted. A visitor comparing an Australian pack with a European one has to do the arithmetic themselves.

Do the per-serving and per-100 g figures round the same way?

They are both rounded, and independently, which is why multiplying up rarely reconciles exactly. Energy is normally declared to the nearest whole kilojoule and kilocalorie, so a 30 g serving of a 1 600 kJ cereal may be printed as 480 kJ while the exact product is 480.0 and a slightly different rounding of the kilocalorie column gives 115 rather than 114.7. Small mismatches of a unit or two are normal, not an error.

How does a manufacturer arrive at the kilojoule number in the first place?

By calculation from the composition, using the conversion factors listed in the regulation: 17 kJ per gram of carbohydrate and of protein, 37 kJ per gram of fat, 29 kJ per gram of ethanol, 8 kJ per gram of fibre. Multiply each analysed nutrient by its factor, add them up, and that sum is the declared energy. Nothing is burned and nothing is measured directly, which is why two products with identical ingredient analyses always declare identical energy.

Kilojoules to Kilocalories