Therms to Kilocalories (thm to kcal)

1 therm equals 25,210.42065 kilocalories (rounded).

1 therm = 25,210.42065 kilocalories

How to convert therms to kilocalories

To convert therms to kilocalories, multiply the number of therms by 25,210.42065. The factor is rounded to 10 significant digits. To go the other way, multiply kilocalories by 0.00003966613703 (rounded).

kilocalories = therms × 25,210.42065

Example: 10 therms = 252,104.2065 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

Therm (thm)

US customaryTraditional unit (still used in some regions)

100,000 BTU (about 105.48 MJ). US natural gas bills are measured in therms.

Gas bills gave the therm its place in daily life. It is defined as 100,000 British thermal units, so its size depends on which BTU is meant. The figure used here, 105,480,400 joules or about 29.30 kWh, is the US therm, built on a BTU defined at 59 degrees Fahrenheit. The European Community version, based on the ISO BTU, is 105,506,000 joules, and the UK value is about 105,505,585 joules.

In the United States, natural gas is billed in therms or in CCF, hundreds of cubic feet. Pipeline companies adopted the decatherm, 10 therms or a million BTU, around 1972 to simplify invoicing, and roughly 1,000 cubic feet of gas holds about one decatherm.

Britain moved the other way. Regulations replaced therms with joules from 1999, retail customers now see kilowatt-hours, and only the wholesale market still quotes pence per therm. The EIA lists one therm as 100,000 Btu, and the Btu itself is the heat needed to warm a pound of water by one degree Fahrenheit.

1 therm = 105,480,400 joules (exactly).

Sources: Wikipedia: Therm; EIA: British thermal units (Btu); Wikipedia: British thermal unit

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.