kcal, cal and kJ converter
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The calorie printed on your food is a thousand times bigger than the calorie in a physics textbook. That is the whole confusion.
Two calories, one word
The small calorie is the energy needed to warm one gram of water by one degree Celsius. It is a tiny amount, used in chemistry. The kilocalorie is a thousand of those, and it is what nutrition has always meant.
Food labels write it as Calories with a capital C, or as kcal, and both mean the same thing. So a 250 calorie snack is 250 kcal, which is 250,000 small calories. Nobody writes that, which is exactly why the confusion survives.
Kilojoules, and where you meet them
The kilojoule is the metric unit for energy, and one kilocalorie equals 4.184 of them. Australia and New Zealand label food in kilojoules. The European Union prints both. The United States and the United Kingdom lead with calories.
A rough shortcut for reading an Australian label: divide kilojoules by four and you are within five percent of the calorie figure.
The numbers worth memorising
One kcal is 1,000 cal and 4.184 kJ. A thousand kilojoules is about 239 calories. A typical daily intake of 2,000 calories is 8,368 kilojoules, which is why Australian labels look alarming to visitors until the unit registers.
Stop doing this by hand
Whatever the unit on the packet, photographing the plate skips the arithmetic entirely.
Get Kalixo free on the App StoreQuestions people actually ask
Is a calorie the same as a kilocalorie?
On food, yes. The Calorie on a nutrition label is a kilocalorie. In physics they differ by a factor of a thousand, which is the source of nearly every misunderstanding.
How do I convert kJ to calories in my head?
Divide by four. It slightly overestimates, since the exact divisor is 4.184, but it is close enough to compare two products in a shop.
Why does Australia use kilojoules?
It adopted the international metric standard for energy. Kilojoules are the scientifically correct unit, calories are the historically familiar one.
Which unit should I track in?
Whichever your food labels use, so you never convert. Mixing units mid-week is how people end up off by a factor of four.