is a term applicable either to the gram calorie or the kilocalorie. The gram calorie is defined as the amount of heat required at a pressure of one atmosphere to raise the temperature of one gram of water one degree Celsius at 15°C. The kilocalorie is the unit used to express the energy value of food; it is defined as the amount of heat required at a pressure of one atmosphere to raise the temperature of one kilogram of water one degree Celsius; it is equal to 1000 gram calories.

Also see energy.