The exact definitions
1 kcal = 1,000 cal (small/gram calories) 1 kcal = 1 Cal (food Calorie, capital C) 1 kcal = 4.184 kJ (kilojoules) 1 kcal = 4,184 J (joules)
Common conversions
| kcal | cal | kJ |
|---|---|---|
| 100 | 100,000 | 418 |
| 250 | 250,000 | 1,046 |
| 500 | 500,000 | 2,092 |
| 1,000 | 1,000,000 | 4,184 |
| 2,000 | 2,000,000 | 8,368 |
| 2,500 | 2,500,000 | 10,460 |
When you actually need kilojoules
Australian and New Zealand labels lead with kilojoules, and European packaging shows both kJ and kcal side by side. That is the conversion worth memorising, because it is a real one: divide kilojoules by roughly four to get approximate calories. An 850 kJ snack is a little over 200 kcal.
Why the small calorie exists at all
The gram calorie is a physics unit — the energy needed to raise one gram of water by one degree Celsius. It is far too small to describe food, so nutrition adopted the kilocalorie and, confusingly, wrote it with a capital C. Once lower-case writing took over, the distinction collapsed, which is the entire reason this conversion gets searched in the first place.
If you are here because a label and an app disagree, the unit is almost never the cause. Work out your daily calories to get a target worth comparing against, or read how to read your calorie number.
Sources
- International System of Units (SI): 1 calorie (thermochemical) = 4.184 J exactly; 1 kcal = 1,000 cal.
- EU Regulation No 1169/2011 — requires energy declaration in both kJ and kcal on packaged food.
