kilogram calorie, large calorie: A unit of energy 1000 times larger than the gram calorie. It is equivalent to the gram kilocalorie, approximately 4.2 kilojoules.
gram calorie, small calorie: a non-SI unit of energy, equivalent to approximately 4.2 joules. This unit was widely used in chemistry and physics, being the amount of energy needed to raise the temperature of 1 gram of water by 1 °C.
calorie (amount of heat to raise 1 gram of water by 1°C)