Small calorie

Small Calorie

The small calorie or gram calorie (symbol: cal) is a unit of energy in the International System of Units. It is defined as the approximate amount of energy needed to raise the temperature of one gram of water by one degree Celsius at a pressure of one atmosphere.

Definition and Conversion

The small calorie is not an SI unit, which uses the joule as the unit of energy. However, it remains in common use for the amount of energy obtained from food. One small calorie is approximately equal to 4.184 joules. The large calorie, or kilocalorie (symbol: Cal), is 1000 small calories, and is often used to express the energy content of foods.

Usage

In the context of nutrition, people often refer to calories when they mean kilocalories, leading to some confusion. The "calories" that are counted in dietary intake and expenditure are actually kilocalories, so a food item that "contains 100 calories" actually contains 100 kilocalories, or 100,000 small calories.

Measurement

The small calorie was first defined by Nicolas Clément in 1824 as a unit of heat energy. It entered French and English dictionaries between 1841 and 1867. The word comes from Latin calor meaning heat.

See also

• Large calorie
• Food energy
• Basal metabolic rate
• Metabolism