Guide · Updated 17 September 2026
kJ to calories, how to read an Australian menu board
Divide by four. That's the whole trick. A menu board that says 2,600 kJ is about 650 calories. The exact number is 4.184 kJ to a calorie, so dividing by 4.2 is closer, but four is good enough to make a decision at a drive through and it's the one you'll actually do in your head.
A Big Mac is 2,598 kJ on the board at Maccas. Divide by four, you get about 650. The real figure is 621 calories. Close enough.
Why Australia uses kJ
Because it's the metric unit for energy and Australian food labelling law uses it. Every packaged food here shows kilojoules, so when the state governments started making big chains put energy on their menu boards, they used the same unit. That's it. There's no nutritional reason, it's just the unit we picked.
The problem is that nobody thinks in kilojoules. Every fitness app, every diet plan and every conversation you've ever had about food is in calories. So the number on the board is technically there and practically useless, which is one of the reasons I built the app. Every item in it shows both.
The 8,700 kJ on the menu board
You'll see "the average adult daily energy intake is 8,700 kJ" printed on menu boards and packaging. That's about 2,080 calories. It's the reference figure the labelling rules use for the percentage on the back of a packet.
It's not your number. A small woman who sits at a desk needs less. A big bloke who trains needs more. To work out your own, use the maintenance calorie calculator. But it's a useful yardstick for reading a board. If a meal is 4,000 kJ, that's nearly half the reference day in one sitting, and you don't need to convert it to know that's a lot.
Worked examples
A few common items with both numbers, so you can see how the maths lands.
| Item | kcal | kJ | Protein g | Fat g | Carbs g |
|---|---|---|---|---|---|
| Big Mac McDonald's | 621 | 2,598 | 28.7 | 34.4 | 46.5 |
| Whopper Hungry Jack's | 582 | 2,435 | 28.1 | 45.2 | 46.6 |
| Zinger Burger KFC | 448 | 1,874 | 26.2 | 22.5 | 34.4 |
| Grilled Chicken Burrito Guzman y Gomez | 773 | 3,234 | 48.3 | 23.5 | 91.0 |
| Bacon & Egg McMuffin McDonald's | 282 | 1,180 | 17.6 | 11.8 | 25.3 |
| Assorted Sashimi Sushi Hub | 191 | 799 | 32.1 | 2.3 | 9.9 |
The Whopper at 2,435 kJ is 582 calories. The Zinger at 1,874 kJ is 448. The GYG grilled chicken burrito at 3,234 kJ is 773, and that one's a good example of why you convert. Three thousand and something kilojoules doesn't sound like much. Nearly 800 calories does.
Going the other way
If you know your calorie target and want it in kJ, multiply by 4.2. A 1,800 calorie day is about 7,500 kJ. A 500 calorie meal is about 2,100 kJ. So if you're standing at a board and you've decided lunch is 500 calories, you're looking for anything under about 2,100.
The mistake people make
Reading the kJ figure as if it were calories. It happens more than you'd think, usually the other way, where someone sees "2,600" on a board, thinks "that can't be calories, it must be fine", and doesn't do the division. It's 620 calories. Or they see 1,200 on a McMuffin, think that's a huge breakfast, and skip it, when it's actually 282 calories and one of the best things on the menu.
Do the division. Or use the kJ to calories converter and let it do it for you.
FAQ
How many kJ in a calorie?
4.184, which most people round to 4.2. To go from kJ to calories, divide by 4.2. To go from calories to kJ, multiply by 4.2. Dividing by four in your head gets you close enough to decide.
How many calories is 8,700 kJ?
About 2,080. It's the reference daily intake printed on Australian food labels and menu boards, not a recommendation for you personally.
How many kJ in a Big Mac?
2,598 kJ, which is 621 calories. That's McDonald's Australia's own published figure and the app tracks it against the live menu.