Why are calories shown in (kcal) and not (cal) when K is shorthand for Kilo (1000) ?


So for example, I’m looking at a pack of sausages, the text says “reference intake of an average adult is 8400kJ / 2000 kcal – but I am reading this as 2 million calories, since K is short for kilo which means 1000?

In: 420

Isn’t this a Calorie vs calorie thing? ie big C Calorie being 1kcal. But 1 small c calorie isn’t really that useful outside of actual science so we just don’t use it. … I think

People use Calorie (note the capital) and Kilocalorie interchangeably. The calorie (small c) is 1/1000 of a Calorie.

So it’s both. 2000 big Calories (which is the actual measurement everyone is used to dealing with), 2 million small calories (which is arguably more true to the definitions, but nobody outside of particularly ornery chemists has any real use for the unit). Since nobody really uses the small calorie for anything, people don’t know/forget they’re two different things and also get sloppy about distinguishing between the two.

A calorie is the amount of energy needed to heat a gram of water 1°C whereas a kilogram calorie relates to heating a kilogram of water and so is 1000 times bigger. The larger unit can use the symbol “kcal” or “Cal” (with an uppercase C) and its use is largely restricted to food science. Calling a kilogram calorie simply a “Calorie” is also common although, obviously, dangerously ambiguous.

The safest approach, and the one generally used in other sciences, is to stick to the SI standard unit of the joule and its symbol “J”. This has the added advantage of being based only on the metre, second and kilogram, and doesn’t rely on measuring the property of a weird chemical like water.

One calorie is the amount of energy needed to raise the temperature of 1 gram of water through 1° C. This is obviously a very small amount of energy. Therefore we use kilo calories (Kcal) to make the number more easily digestible