Calorie vs Kilocalorie
One food Calorie is one kilocalorie, equal to 1,000 small calories or 4,184 joules.
By Piero Nanni · Last checked
Two units, one word
The small calorie, or gram calorie, is the energy needed to raise one gram of water by one degree Celsius: 4.184 joules. The large Calorie, or kilocalorie, does the same for a kilogram of water and is therefore 1,000 times bigger.
Nutrition labelling settled on the large one because the small one produces unwieldy numbers. A slice of bread holds about 80,000 small calories, which is why it is written as 80 Calories instead.
| Unit | Symbol | In joules | Where it appears |
|---|---|---|---|
| Small calorie | cal | 4.184 J | Physics and chemistry |
| Kilocalorie | kcal | 4,184 J | Nutrition labels worldwide |
| Food Calorie | Cal | 4,184 J | US nutrition labels and everyday speech |
| Kilojoule | kJ | 1,000 J | EU, Australian and NZ labels |
The capital C convention does not hold up
The formal convention is that a capital C means the kilocalorie and a lowercase c means the small calorie. In practice almost nobody outside a textbook observes it, and the distinction disappears entirely at the start of a sentence or in an all-caps heading.
The dependable signal is the number. If a portion of food is listed in the hundreds, those are kilocalories. If a figure runs to the hundreds of thousands, someone has used small calories.
Reading a label in kilojoules
European labels are required to show kilojoules and normally show kilocalories beside them. Australian and New Zealand labels often show kilojoules alone.
To go from kilojoules to kilocalories, divide by 4.184. A 2,000 kcal daily reference is 8,368 kJ, usually printed as 8,400 kJ. Going the other way, multiply kilocalories by 4.184.
Frequently Asked Questions
Is a Calorie the same as a kilocalorie?
Yes. The Calorie on a nutrition label is a kilocalorie, 1,000 small calories.
How many joules in a food Calorie?
4,184 joules, or 4.184 kilojoules.
How do I convert kilojoules to calories?
Divide the kilojoules by 4.184 to get kilocalories, which is what labels call Calories.
Why do EU labels use kilojoules?
The joule is the SI unit of energy, and EU food information rules require energy to be declared in kilojoules, usually alongside kilocalories.