Calorie, abbreviated as card, abbreviated as cal, is transliterated from English. It is defined as the heat required to raise 1 gram of water to 1 degree Celsius at 1 atmospheric pressure; Calorie is a kind of heat unit, which is widely used in nutrition measurement and fitness manuals. The international standard energy unit is joule.

As the legal unit of food calories, joules are widely used in Europe, while calories are used in the United States. Although Joule is the legal unit in China, calories are still widely used in Chinese mainland and Taiwan Province due to its tradition.