To convert kilocalories to calories, divide the number of kilocalories by 1,000. A kilocalorie is known in scientific notation as a large calorie to distinguish it from the basic unit calorie, which is referred to as a small calorie. A calorie is a unit of heat that equals 4.2 joules.
In nutritional contexts, both "calorie" and "kilocalorie" sometimes refer to the same unit; nutrition labels attempt to clear the confusion by capitalizing "Calorie" when it refers to a kilocalorie.
Previously, a calorie was defined as the amount of energy required to raise the temperature of 1 gram of water by 1 degree Celsius at standard pressure and density. This definition was discarded when the joule became the standard unit of energy for the International System of Units.