Ergs to Kilocalories (erg to kcal)

1 erg equals 2.390057361×10⁻¹¹ kilocalories (rounded).

1 erg = 2.390057361×10⁻¹¹ kilocalories

How to convert ergs to kilocalories

To convert ergs to kilocalories, multiply the number of ergs by 2.390057361×10⁻¹¹. The factor is rounded to 10 significant digits. To go the other way, multiply kilocalories by 41,840,000,000.

kilocalories = ergs × 2.390057361×10⁻¹¹

Example: 10 ergs = 2.390057361×10⁻¹⁰ 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

Erg (erg)

CGS & old metricTraditional unit (still used in some regions)

Exactly 10⁻⁷ joules. The energy unit of the old centimeter-gram-second (CGS) system, still used in astrophysics.

Erg takes its name from the Greek ergon, meaning work. Rudolf Clausius proposed that word for a unit of energy in 1864, and in 1873 a British Association committee including Maxwell and Thomson asked that erg be reserved for the energy unit of the centimeter-gram-second system.

It is the work done by a force of one dyne acting through one centimeter, or 1 g cm2/s2. That equals 10 to the power minus 7 joule, 100 nanojoules, which is a very small amount of energy and was a natural size for laboratory experiments of the era.

The erg is not an SI unit, and NIST lists it only as a conversion factor to the joule. It survives mainly in astrophysics and theoretical physics, where Gaussian CGS units remain common, so cosmic energies are still often given in ergs.

1 erg = 1×10⁻⁷ joules (exactly).

Sources: Wikipedia: Erg (unit); Wikipedia: Centimetre-gram-second system of units; NIST SP 811, Appendix B.8 conversion factors

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.