A calorie is the amount of energy (heat) required to raise 1 gram (1 milliliter) of water by 1°C. A kilocalorie (kcal) is the amount of energy required to raise 1 kilogram (1 liter) of water by 1°C. The kilocalorie is the unit used to describe the energy value in food, since the calorie is a relatively small unit of measurement. For example, if a chocolate chip cookie were completely incinerated, the amount of heat energy released would be enough to raise the temperature of one liter of water by approximately 300°C.