Calories (IT) to Kilocalories (cal (IT) to kcal)

1 calorie (IT) equals 0.001000669216 kilocalories (rounded).

1 calorie (IT) = 0.001000669216 kilocalories

How to convert calories (IT) to kilocalories

To convert calories (IT) to kilocalories, multiply the number of calories (IT) by 0.001000669216. The factor is rounded to 10 significant digits. To go the other way, multiply kilocalories by 999.3312315 (rounded).

kilocalories = calories (IT) × 0.001000669216

Example: 10 calories (IT) = 0.01000669216 kilocalories.

The 'calorie' on food labels is really a kilocalorie. The thermochemical calorie (4.184 J) is used here unless marked IT.

About these units

Calorie (IT) (cal (IT))

ScientificHistorical unit (no longer in standard use)

The International Table calorie: exactly 4.1868 joules, slightly larger than the thermochemical calorie. Used in steam tables.

Steam engineers needed a calorie tied to the joule rather than to the behaviour of water, and the Fifth International Conference on the Properties of Steam, held in London in July 1956, fixed one. The result, the International Table calorie, is exactly 4.1868 J, defined as 1.163 milliwatt-hours. An earlier International Steam Table calorie of 1929 was about 4.1860 J, so the 1956 choice slightly adjusted the older figure.

Compared with the thermochemical calorie of 4.184 J, the International Table version is larger by 0.0028 J, or roughly 0.07 percent. That is negligible for cooking but can matter in steam tables and engineering handbooks, where the calorie and its kilocalorie multiple of 4,186.8 J are used. NIST lists both calories as exact values and flags them separately for that reason. The figure used here for this unit is 4.1868 J. Anyone converting data should check which calorie a source assumes before comparing numbers.

1 calorie (IT) = 4.1868 joules (exactly).

Sources: Wikipedia: Calorie; NIST SP 811, Appendix B.8 (energy conversion factors); Wikipedia: Conversion of units of energy

Kilocalorie (kcal)

ScientificTraditional unit (still used in some regions)

1,000 thermochemical calories (4,184 J). The 'Calorie' on food labels in North America.

Marcellin Berthelot separated the gram calorie from the kilogram calorie in 1879, and the American chemist Wilbur Atwater adopted a capital-C Calorie for the large unit in 1887 in a widely read article on the energy in food. Joseph Howard Raymond proposed the term kilocalorie in his 1894 textbook. The two names now describe the same quantity, 1,000 small calories, which at the thermochemical value is 4,184 J or 4.184 kJ.

Food labels carry the unit today, though practice differs by region. North American labels use kilocalories almost exclusively, European labels show kilojoules and kilocalories together under EU Regulation 1169/2011, and Chinese labels give kilojoules only. Typical energy contents are about 9 kcal per gram for fat, about 4 for carbohydrate and protein, and about 7 for alcohol. In electrical terms, 4,184 J works out to about 1.162 watt-hours, since one watt-hour is 3,600 J. NIST also lists a kilocalorie based on the International Table calorie, which is 4,186.8 J.

1 kilocalorie = 4,184 joules (exactly).

Sources: Wikipedia: Calorie (includes kilocalorie); NIST SP 811, Appendix B.8 (energy conversion factors)

Related conversions

See all energy units.