Joules to Calories (IT) (J to cal (IT))

1 joule equals 0.2388458966 calories (IT) (rounded).

1 joule = 0.2388458966 calories (IT)

How to convert joules to calories (IT)

To convert joules to calories (IT), multiply the number of joules by 0.2388458966. The factor is rounded to 10 significant digits. To go the other way, multiply calories (IT) by 4.1868.

calories (IT) = joules × 0.2388458966

Example: 10 joules = 2.388458966 calories (IT).

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

About these units

Joule (J)

Metric (SI)Current unit

The SI unit of energy: the work done by a force of one newton over one meter, or one watt for one second.

James Prescott Joule was born in Salford on 24 December 1818, the son of a wealthy brewer, and later ran the family brewery while treating science as a serious hobby. In June 1845 he told a British Association meeting in Cambridge about his best-known experiment: a falling weight turned a paddle wheel inside an insulated barrel of water, and the water warmed up. Mechanical work turned into heat at a fixed rate, which supported energy conservation and undermined the caloric theory of heat.

The unit came later. On 23 August 1882 Carl Wilhelm Siemens proposed at a British Association meeting that a unit of heat equal to 10 million ergs be named the joule, and in 1889 the second International Electrical Congress adopted it alongside the watt. Joule died that same year. In 1948 the CGPM added that the joule should be preferred to the calorie as the unit of heat, and it entered the SI in 1960.

For scale, one joule is about the energy needed to lift an apple of roughly 102 g by one meter. A 56 g tennis ball moving at 6 m/s carries about one joule of kinetic energy.

The joule is the reference unit for energy on this site.

Sources: Wikipedia: Joule; Wikipedia: James Prescott Joule

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

Related conversions

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