Joules to Therms (J to thm)

1 joule equals 9.48043428×10⁻⁹ therms (rounded).

1 joule = 9.48043428×10⁻⁹ therms

How to convert joules to therms

To convert joules to therms, multiply the number of joules by 9.48043428×10⁻⁹. The factor is rounded to 10 significant digits. To go the other way, multiply therms by 105,480,400.

therms = joules × 9.48043428×10⁻⁹

Example: 10 joules = 9.48043428×10⁻⁸ therms.

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

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

Related conversions

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