The calorie is a pre-SI metric unit of energy. The unit was first defined by Professor Nicolas Clément in 1824 as a unit of heat. This definition entered French and English dictionaries between 1841 and 1867. In most fields its use is archaic, having been replaced by the SI unit of energy, the joule. However, in many countries (USA for one) it remains in common use as a unit of food energy.

CALORIES IN CHOCOLATE PER 100 G:
Milk chocolate: 588
Dark Chocolate: 544
Cocoa powder: 452
Cocoa: 417
Toffee: 399
Hard candies: 327