calorie (International Table)
Energyexact by definition
The International Table calorie is exactly 4.1868 joules, defined in 1956 by fixing the IT calorie against the IT kilowatt-hour rather than against any measurement of water. It is the calorie used in steam tables, refrigeration and most of European heating practice.
Watch out: This site's plain "calorie" is the thermochemical calorie of exactly 4.184 J, the one chemistry and nutrition use. The two differ by 0.07 percent, which is nothing in a diet and is enough to matter in a heat balance carried to four figures. A third value, the 15 °C calorie of about 4.1855 J, appears in older physics texts. If a document does not say which calorie it means, the field usually decides: thermochemical for chemistry and food, IT for steam and HVAC.
| 1 cal IT | 4.1868 J |