Therms to British Thermal Units (thm to BTU)
1 therm equals 99,976.12898 British thermal units (rounded).
How to convert therms to British thermal units
To convert therms to British thermal units, multiply the number of therms by 99,976.12898. The factor is rounded to 10 significant digits. To go the other way, multiply British thermal units by 0.00001000238767 (rounded).
British thermal units = therms × 99,976.12898
Example: 10 therms = 999,761.2898 British thermal units.
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)
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
British Thermal Unit (BTU)
The International Table BTU, exactly 1,055.05585262 joules. The energy to heat one pound of water by one degree Fahrenheit; used for heating, cooling and gas appliances in the US.
Few energy units come in as many versions as the British thermal unit. It was defined as the heat needed to raise one pound of liquid water by one degree Fahrenheit, but because water's heat capacity shifts slightly with temperature, definitions differ by up to 0.5 percent: about 1,054.35 J for the thermochemical Btu, 1,054.80 J at 59 degrees Fahrenheit (used for American natural gas pricing), 1,054.68 J at 60 degrees (mainly Canadian), and 1,059.67 J at 39 degrees. A 1942 note suggests the term apparently arose in the United States and was later adopted in Britain.
The version on this site is the International Table Btu, about 1,055.06 J, which comes from the international steam table conferences that tied heat units to the joule. Joule's own 1850 experiments gave 772.692 foot-pounds of work per Btu, the number that first linked heat to mechanical effort.
Today the Btu survives in natural gas pricing (MMBtu means a million Btu), US building energy reporting, and equipment ratings in Btu per hour. One ton of air-conditioning is 12,000 Btu/h, or 3.52 kW. A single wooden kitchen match burning releases about one Btu.
1 British thermal unit = 1,055.055853 joules (approximately).
Sources: Wikipedia: British thermal unit; Wikipedia: James Prescott Joule
Related conversions
- British thermal units to therms (reverse)
- Therms to joules
- Therms to kilojoules
- Therms to watt-hours
- Therms to kilowatt-hours
- Therms to calories
- Therms to kilocalories
- Joules to British thermal units
- Kilojoules to British thermal units
- Watt-hours to British thermal units
- Kilowatt-hours to British thermal units
- Calories to British thermal units
- Kilocalories to British thermal units
- Megajoules to British thermal units
- Gigajoules to British thermal units
- Megawatt-hours to British thermal units
- Foot-pounds to British thermal units
- Millijoules to British thermal units
- Electronvolts to British thermal units
See all energy units.