Simply put, the energy or heat of 1 calorie can raise the temperature of 1 gram of water at one atmospheric pressure 1 degree Celsius, and 1 calorie is about 4. 1859 Joule (Joule is a commonly used energy unit in physics).

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Generally, it can be found from the food composition table, or it can be accurately measured by calorimeter. Put the sample to be measured into the combustion chamber of calorimeter for complete combustion, and all the released energy is absorbed by water. One millilitre of water rises by one degree at normal pressure, which needs to absorb 4. 187 joules. Record the changes of water quality and water temperature, and make corresponding conversion.

The conversion between them is: 1 calorie =4. 186 joules; 1 kcal = 1 kcal = 1000 kcal = 1000 calories =4 186 joules =4. 186 kj.