What are the differences between Calories, calories, and kcals?
Why do we have different terms to describe the same concept?
In what cases is it useful to use one unit of measurement over the other?
One calorie (with a lower case c) is the amount of energy required to heat 1 gram of water by 1°C. A kilocalorie is 1000 calories, and Calorie (with a capital C) and kilocalorie (Kcal) are synonyms. On food labels, nutrition facts are in terms of kilocalories/Calories. (Wikipedia)
Just like with grams vs. kilograms, units are used in a way that the number most readable. Putting nutrition labels in calories would take up quite a bit of extra space. I'm not sure how the Calorie/kilocalorie synonym came about, but I can guess it was for convenience. We use kilocalories much more frequently than calories for every day measurement, and kilocalories is quite a cumbersome word.
It is still confusing, because both terms (with and without the kilo- prefix) covers the same amount, and it is only a capital letter that differentiates beween 1 and 1000.
This would be equal to having Gram (with a capital letter) and kilogram being the same, and gram being 1/1000 of that. I hopy everyone can see how stupid that would be, and this is exactly how stupid the Calorie term is.
There should only be calories and kilocalories. Calories (with a capital letter) does not fit in.
Besides, most food products list the energy contents at kcal and not Cal, which give the same short numbers. You never need to see 70000 instead of 70 even if Calories are dropped.
A kilocalorie is equal to 1000 calories. I discovered this a while back. Although the labels on food packages display energy as calories, the actual metric is supposed to be kilocalories.
So that apple you may have just ate has 70000 calories or 70 kilocalories.