Calories

The calorie is a unit of energy defined as the amount of heat needed to raise a quantity of water by one degree of temperature. There are two versions of the unit in use, which has led to some confusion. It is historically defined as the amount of heat energy needed to raise the temperature of one gram of water by one degree Celsius. This is now known as the small calorie and is spelled with a lower case ''c''. Today it is most widely used in nutrition as the large Calorie, where it is spelled with a capital ''C'' and is defined as the amount of heat needed to raise the temperature of one kilogram of water by one degree Celsius. ie the Calorie in nutrition is equal to 1000x the calorie used in traditional physics.