Megajoules to Kilocalories (MJ to kcal)

1 megajoule equals 239.0057361 kilocalories (rounded).

1 megajoule = 239.0057361 kilocalories

How to convert megajoules to kilocalories

To convert megajoules to kilocalories, multiply the number of megajoules by 239.0057361. The factor is rounded to 10 significant digits. To go the other way, multiply kilocalories by 0.004184.

kilocalories = megajoules × 239.0057361

Example: 10 megajoules = 2,390.057361 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

Megajoule (MJ)

Metric (SI)Current unit

One million joules. Used for fuel energy content and natural gas billing in many countries.

Picture a one-tonne car moving at 44.7 m/s, about 100 miles per hour: its kinetic energy is roughly one megajoule. Because the joule was originally conceived in 1882 as 10 million ergs, a megajoule is 10 to the 13th ergs, a figure that shows how little the old CGS unit suited everyday work and why the joule won out.

Food provides a more familiar benchmark. A Snickers bar of 280 food calories holds about 1.2 MJ, and a day's 2,000 food calories for a moderately active woman come to about 8.4 MJ. A kilowatt-hour of electricity is exactly 3.6 MJ, and exploding a kilogram of TNT releases about 4.2 MJ.

In other words the megajoule sits at the scale of a single serving of fuel, food or electricity, which is why it turns up in energy-content tables where joules would give unwieldy numbers.

1 megajoule = 1,000,000 joules (exactly).

Sources: Wikipedia: Joule; Wikipedia: Orders of magnitude (energy); Wikipedia: Kilowatt-hour

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.