Cal, kilocalorie, kcal, calorie, and kilojoule are all units of heat. 1 calorie is what is required to raise the temperature of 1 gram of water by 1 degree Celsius after burning the food we eat. Heat, kilocalorie, is the heat required to raise the temperature of 1 liter of water by 1 degree Celsius. Kilocalorie is also called kcal. \r\nA calorie (abbreviated as "calorie") is defined as the amount of heat required to raise 1 gram of water by 1 degree Celsius at 1 atmosphere of pressure. 1 kcal is equal to 1000 calories, about 4184 joules. The calories of fat are about 900 calories per 100 grams; the calories of sugar and protein are only 400 calories per 100 grams. \r\nThe conversion between them is:\r\nKcal = kcal\r\n1 kcal = 1000 calories\r\n1 kJ = 1000 joules\r\n1 kcal/1 kcal = 1000 Calorie\r\n1 kcal/1 kcal=4.184 kilojoules (kJ)\r\n1 cal=4.182 joules