
[French, from Latin calor, heat. See caloric.]
| callus, caliph, calibre | |
| cambric, camellia, cameo |
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heat energy 4.1868 J (3.968 322 93~ × 10-3 B.t.u.), but also thermochemical calorie calth = 4.184 J.
Although widely known as a unit for indicating the energy content of foodstuffs (and hence, to some extent, their ‘fattening power’), the calorie is technically a measure of heat energy. Its use in nutrition corresponds to its use in physics, both being a measure of energy; however, the ‘calorie’ of the food packet is usually a kilocalorie or kilogram-calorie of 1 000 calories, reflecting a like ambiguous use in physiology. Sometimes distinguished by capitalization as Calorie, the latter is more clearly the large calorie or grand calorie with the true unit as the small calorie, petit calorie, or, more properly, the gram-calorie.
Defined in 1880 as the energy required to raise the temperature of 1 gram of water by 1 Celsius degree (i.e. 1 K) without further qualification, the term required an acknowledgement of the reference temperature for any precise use, since the amount is dependent on starting temperature. This is denoted by a suffix, e.g. cal15 denotes the rise from 14.5 to 15.5°C; calmean denotes the mean per degree over the range 0 to 100°C.
| international steam calorie calIT | = 4.186 74~ J, |
| mean calorie calmean | = 4.190 02~ J |
| 4°C calorie cal4 | = 4.204 5~ J (water at its densest) |
| 15°C calorie cal15 | = 4.185 5~ J (15°C = cool indoors) |
| 20°C calorie cal20 | = 4.181 90~ J (20°C = warm indoors) |
A unit of energy used to express the energy yield of foods and energy expenditure by the body. Name coined by Atwater in 1895. One calorie (cal) is the amount of heat required to raise the temperature of 1 g of water through 1 ° C (from 14.5-15.5 ° C). Nutritionally the kilocalorie (1000 calories) is used (the amount of heat required to raise the temperature of 1 kg of water through 1 ° C), and is abbreviated as either kcal or Cal to avoid confusion with the cal.
The calorie is not an SI unit, and correctly the joule is used as the unit of energy, although kcal are widely used. 1 kcal = 4.18 kJ; 1 kJ = 0.24 kcal.
Despite an international convention which agreed to use the joule (J) as the standard unit for energy, work, and heat, the calorie is the unit most commonly used in written work about nutrition. One calorie is the amount of heat required to raise the temperature of 1 g of water through 1°C (more precisely, from 14.5°C to 15.5°C). It is easy to convert calories into joules, as one calorie equals 4.2 joules (more exactly, 4.184 joules). These units are very small in relation to the energy used by a person, so it is usual to use units 1000 times larger. These should be called kilocalories (often written as Calorie), but most diet and exercise books use ‘calories’ to mean kilocalories; so a 1000 calorie diet is really a diet that provides 1000 kilocalories a day.
[KAL-uh-ree] A unit measuring the energy value of foods, calibrated by the quantity of heat required to raise the temperature of 1 gram of water by one degree celsius at a pressure of one atmo- sphere. The four sources from which calories are obtained are alcohol, carbohydrates, fats and proteins however all these sources are not equal. For example, fat packs a hefty 9 calories per gram, over twice as much as the 4 calories per gram carried by both carbohydrates and proteins. Alcohol has 7 calories per gram, almost as many as fat. Clearly, fats and alcohol have a much higher caloric density than carbohydrates and proteins, so it's obvious that a 6-ounce serving of steak will be much more expensive calorically than 6 ounces of cauliflower.
Calor means heat, and a calorie is defined as the amount of heat which will raise the temperature of one gram of water by 1°C. The Calorie (kilocalorie, kcal) is 1000 calories — a more useful unit and widely used. In a ‘calorimeter’ a substance can be combusted in the presence of oxygen, to measure the amount of heat generated per gram. From such basic measurements, and by extrapolation to mixtures of different ingredients, the ‘calorie count’ can be applied as a measure of the energy derivable from a food source. Kcals are also the traditional units for the body's metabolic rate: the energy output or expenditure in kcal/min. Attempts to supplant it by the SI (Systeme Internationale) unit, the kilojoule (energy defined in electrical terms) have only partially succeeded; the energy content of food is usually quoted in both (1 kcal = 4.2 kJ).
— Stuart Judge
See dieting; energy balance; metabolism.
The heat required to raise the temperature of 1 gram of water 1°C; now called a small calorie. A large calorie is equal to 1000 small calories, i.e. a kilocalorie.
Unit of work and energy. One calorie is the amount of heat required to raise the temperature of 1 g of water by 1°C at normal pressure. Although it has been replaced by the joule in the SI system, the calorie is still widely used, especially in describing energy values of food and exercise expenditure. Physiologists tend to use the kilocalorie (equal to 1000 cal), sometimes referred to as the Calorie (Cal) to distinguish it from the calorie.
The calorie is a unit for measuring heat energy, and it is usually used as the unit for food energy and of energy expenditure. Media and lay attention to food, exercise, and health, as well as the greater prevalence of obesity during the past few decades, has resulted in a cultural preoccupation with caloric intake and expenditure in industrialized nations. Heat is that which produces a change in temperature. Heat was formerly regarded as a substance called "caloric," but it came to be viewed as the random motion of molecules.
The calorie has traditionally been defined as the amount of heat required to raise the temperature of 1 gram of water by 1.8°F (1.0°C), usually defined as from 58.1°F to 59.9°F (14.5°C to 15.5°C), under normal atmospheric conditions. Because electrical measurements can be standardized more accurately than heat measurements, a calorie is officially defined as equivalent to 4.186 joule. A joule is defined, in "force × distance" units, as 1 Newton meter, which is equal to (1 kg m/s2) × (1m) or 1 kg m2/s2. Energy values are expressed as joules when the Système International d'Unités, which is recommended for all scientific purposes, is required.
Food energy values and energy expenditures are commonly expressed as the number of kilocalories (kcal). One kcal is equal to 1000 calories or 4.186 kJ or 0.004186 MJ. Although the terms "calorie" and "large calorie" have frequently been used in place of kilocalorie in the nutrition literature and for food labeling purposes, these alternative terms are confusing, and their use is discouraged.
Measurement of Energy Values of Foods
The energy in foods is present as chemical energy; it can be measured by the heat evolved when the food is oxidized or combusted. Although energy transformations normally involve friction and heat conduction, which cause the changes of one form of energy to another to be incomplete, various forms of energy normally can be converted completely to heat. The caloric value of a food may be determined by burning weighed samples of the food in an oxygen atmosphere in an apparatus called a calorimeter, which is designed to allow measurement of the heat released by combustion of the fuel or food. The total amount of heat produced or consumed when a chemical system changes from an initial state to a final state is independent of the way this change is brought about (the law of Hess or the law of constant heat sums). Thus the complete oxidation of a compound, such as glucose, to CO2 and H2O produces the same amount of heat whether the process is carried out in a calorimeter or by metabolism within the body.
Heats of combustion are not accurate reflections of the amount of energy available to the body, however, because the body does not completely absorb and metabolize ingested nutrients. The energy lost in the excreta (feces and urine) must be subtracted from the total energy value of the food to obtain the amount of energy available to the body from consumption of the food. The caloric values of foods reported in food composition tables are "physiological fuel values," also referred to as "available energy" or "metabolizable energy" values. They are not total energy values.
Physiological Fuel Values of Foods
The physiological fuel value of a food or a food component may be determined by measuring the heat of combustion of the food in a calorimeter and then multiplying the heat of combustion by correction factors for incomplete digestion and incomplete oxidation of the food in the body. In about 1900, Wilbur Olin Atwater and his associates at the Connecticut (Storrs) Agriculture Experiment Station used this approach to determine the physiological fuel values of a number of food components (i.e., the protein, fat, and carbohydrate isolated from various foods). They determined factors appropriate for individual foods or groups of foods, and they proposed the general physiological fuel equivalents of 4.0, 8.9, and 4.0 kcal per gram of dietary protein, fat, and carbohydrate respectively for application to the mixed American diet. These factors are commonly rounded to 4, 9, and 4 kcal per gram (17, 36, and 17 kJ per gram) respectively for protein, fat, and carbohydrate. The conversion factors determined by Atwater and his associates remain in use in the twenty-first century, and energy values of foods are calculated using these factors. The energy values (physiological fuel values) reported in food composition tables are commonly estimated by determination of the proximate composition of each food (i.e., the water, protein, fat, carbohydrate, and ash contents) followed by multiplication of the amount of each energy-yielding component by the appropriate conversion factor.
Bibliography
Kleiber, Max. The Fire of Life: An Introduction to Animal Energetics. New York: Wiley, 1961.
Kriketos, Adamandia D., John C. Peters, and James O. Hill. "Cellular and Whole-Animal Energetics." In Biochemical and Physiological Aspects of Human Nutrition, edited by Martha H. Stipanuk. Philadelphia: Saunders, 2000.
Merrill, A. L., and B. K. Watt. Energy Values of Foods . . . Basis and Derivations. USDA Agriculture Handbook No. 74. Washington, D.C.: U.S. Government Printing Office, 1973.
—Martha H. Stipanuk
To convert from gram-calorie (mean) to:
Btu (mean),
multiply by .00396832.
horsepower-hour,
multiply by 1.55961E-06.
horsepower-hour (metric),
multiply by 1.58124E-06.
joule,
multiply by 4.1868.
kilowatt-hour,
multiply by 1.163E-06.
Related measurements:
Many high calorie foods have a lot of fat in them as well.
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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.
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| kilobase, kilo+, killer-cell helper factor | |
| kilodalton, kilogram, kilogram calorie |
Any of several units of heat defined as the amount of heat required to raise the temperature of 1 gram of water by 1 degree Celsius (1°C) at a specified temperature. The calorie used in chemistry and biochemistry is equal to 4.184 joules. Symbol cal.
In referring to the energy content of foods it is customary to use the ‘large calorie’, which is equal to 1 kilocalorie (kcal), 1000 cal. Every bodily process—the building up of cells, motion of the muscles, the maintenance of body temperature—requires energy, and the body derives this energy from the food it consumes. Digestive processes reduce food to usable fuel, which the body burns in the complex chemical reactions that sustain life.
The amount of heat required to raise 1 g of water 1° C at atmospheric pressure, also called gram calorie or small calorie. A great calorie, or kilocalorie, consists of 1000 small calories. The kilocalorie is the unit used to denote the heat expenditure of an organism and the fuel or energy value of food.

The calorie is a pre-SI metric unit of energy. It was first defined by Nicolas Clément in 1824 as a unit of heat, entering French and English dictionaries between 1841 and 1867.[1] In most fields its use is archaic, having been replaced by the SI unit of energy, the joule. However, in many countries it remains in common use as a unit of food energy.
Definitions of a calorie fall into two classes:
The gram calorie is not used in nutritional contexts. Instead, the large calorie is used. In this context calorie and kilocalorie are equivalent.
In an attempt to avoid confusion, the large calorie is sometimes written as Calorie (with a capital C). This convention, however, is not always followed, and not explained to the average person clearly (and is sometimes ambiguous, such as at the beginning of a sentence). Whether the large or small calorie is intended often must be inferred from context. When used in scientific contexts, the term calorie refers to the small calorie; it is often encountered in contexts such as bond and conformational energies in molecular modeling.[3]
The energy needed to increase the temperature of a given mass of water by 1 °C at atmospheric pressure depends on the starting temperature and is difficult to measure precisely. Accordingly, there have been several definitions of the calorie. The two perhaps most popular definitions used in older literature are the 15 °C calorie and the thermochemical calorie.
The conversion factors used to convert calories to joules are numerically equivalent to expressions of the specific heat capacity of water in joules per gram or kilogram.
| Name | Symbol | Conversions | Notes |
|---|---|---|---|
| Thermochemical calorie | calth | ≡ 4.184 J | [4] |
| 4 °C calorie | cal4 | ≈ 4.204 J
≈ 0.003985 BTU ≈ 1.168×10−6 kWh ≈ 2.624×1019 eV |
the amount of energy required to warm one gram of air-free water from 3.5 °C to 4.5 °C at standard atmospheric pressure. |
| 15 °C calorie | cal15 | ≈ 4.1855 J
≈ 0.0039671 BTU ≈ 1.1626×10−6 kWh ≈ 2.6124×1019 eV |
the amount of energy required to warm one gram of air-free water from 14.5 °C to 15.5 °C at standard atmospheric pressure (101.325 kPa). Experimental values of this calorie ranged from 4.1852 J to 4.1858 J. The CIPM in 1950 published a mean experimental value of 4.1855 J, noting an uncertainty of 0.0005 J.[4] |
| 20 °C calorie | cal20 | ≈ 4.182 J
≈ 0.003964 BTU ≈ 1.162×10−6 kWh ≈ 2.610×1019 eV |
the amount of energy required to warm one gram of air-free water from 19.5 °C to 20.5 °C at standard atmospheric pressure. |
| Mean calorie | calmean | ≈ 4.190 J
≈ 0.003971 BTU ≈ 1.164×10−6 kWh ≈ 2.615×1019 eV |
1⁄100 of the amount of energy required to warm one gram of air-free water from 0 °C to 100 °C at standard atmospheric pressure. |
| International Steam Table calorie (1929) | ≈ 4.1868 J
≈ 0.0039683 BTU ≈ 1.163×10−6 kWh ≈ 2.6132×1019 eV |
1⁄860 international watt hours = 180⁄43 international joules exactly.[5] | |
| International Steam Table calorie (1956) | calIT | ≡ 4.1868 J
≈ 0.0039683 BTU ≈ 1.163×10−6 kWh ≈ 2.6132×1019 eV |
1.163 mW·h = 4.1868 J exactly. This definition was adopted by the Fifth International Conference on Properties of Steam (London, July 1956).[4] |
| IUNS calorie | ≡ 4.182 J
≈ 0.003964 BTU ≈ 1.162×10−6 kWh ≈ 2.610×1019 eV |
This is a ratio adopted by the Committee on Nomenclature of the International Union of Nutritional Sciences.[6] |
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Dansk (Danish)
n. - (gram)kalorie, (kilo)kalorie
Nederlands (Dutch)
calorie, warmte
Français (French)
n. - (Phys) calorie
Português (Portuguese)
n. - caloria (f)
Español (Spanish)
n. - caloría
中文(简体)(Chinese (Simplified))
卡路里
中文(繁體)(Chinese (Traditional))
n. - 卡路里
日本語 (Japanese)
n. - グラムカロリー, 平均カロリー, カロリー, これに相当する食物, 国際表カロリー, 熱量
العربيه (Arabic)
(الاسم) سعرة حراريه
עברית (Hebrew)
n. - קלוריה, חומית
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