Calorie (Cal for short), transliterated from English Calorie, is defined as the heat required to raise 1 gram of water to 1 degree Celsius at 1 atmospheric pressure; Calorie is an energy unit, which is still widely used in nutrition measurement and fitness manual.

The international standard unit of energy 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 Chinese mainland and Taiwan Province Province, it is still widely used in Chinese mainland and Taiwan Province Province because of tradition.

Calories are units of energy. We often associate calories with food, but in fact they apply to anything that contains energy.

Most of us associate calories with what we eat or drink, such as "This soda contains 200 calories". In fact, the calories listed on food packaging are calories, and the capital letter C is also marked, which is equivalent to the heat required to raise 1 000 grams of water from 14.5 degrees Celsius to 15.5 degrees Celsius at1atmospheric pressure, which is about equal to the internal energy of 4 186 joules.