A worked example
A label showing 836 kJ per 100 g is 200 kcal per 100 g, and a 75 g portion comes to 150 kcal.
How kJ and kcal relate
One kilocalorie is 4.184 kilojoules. Divide kJ by 4.184 to get kcal, or multiply kcal by 4.184 to go the other way. Dividing by 4 in your head gets you within about 5%, which is close enough to compare two yoghurts in the shop.
Labels round both numbers separately, so the converted value can be a calorie or two away from the kcal printed beside it. Neither one is wrong.
Why “calories” on a menu means kcal
The calorie in everyday food talk is the kilocalorie, sometimes written Calorie with a capital C. A “200 calorie” snack is 200 kcal, or about 837 kJ. Australia and New Zealand label in kJ first, and EU labels carry both.
kJ to kcal table
The left pair runs kilojoules to kilocalories, the right pair the other way. 8400 kJ and 2000 kcal are the reference intake EU labels measure against.
| kJ | kcal | kcal | kJ |
|---|---|---|---|
| 100 | 24 | 50 | 209 |
| 250 | 60 | 100 | 418 |
| 400 | 96 | 150 | 628 |
| 500 | 120 | 200 | 837 |
| 750 | 179 | 250 | 1,046 |
| 1,000 | 239 | 300 | 1,255 |
| 1,500 | 359 | 400 | 1,674 |
| 2,000 | 478 | 500 | 2,092 |
| 2,500 | 598 | 600 | 2,510 |
| 8,400 | 2,008 | 2,000 | 8,368 |
Questions people ask
How many kcal is 1000 kJ?
About 239 kcal. Divide by 4.184.
Is a kilocalorie the same as a calorie?
On food, yes. Scientifically a calorie is a thousandth of a kilocalorie, but no label means that one.
Do I need both numbers?
No. Pick whichever unit you track in and stick with it. The nutrition label calculator does the rest of the label too.