British thermal unit (Btu)



Amount of heat required to raise the temperature of one pound of water (at or near 39.2 degrees Fahrenheit) by one degree Fahrenheit in practical terms, the amount of heat generated by one lighted stick of match. One Btu is equal to about 252 small calories or 0.252 kilocalories, 778.17 foot pounds, or 1055.06 joules. One pound of air-dried wood generates about 7,000 Btu, a gallon of liquid propane (a hydrocarbon) about 92,000 Btu, a gallon of fuel-oil about 140,000 Btu, one barrel of gasoline about 5.25 million Btus, an average ton of coal about 20 million Btu, and one kilowatt-hour of electricity about 3,400 Btu. Despite its name, this non-metric unit is used more often in the US, Canada, and Caribbean than in Britain (or rest of the world) where calorie is preferred. Used also as a unit of measurement for natural gas prices (1,034 Btu = 1 cubic-foot of natural gas). One Btu per hour equals 0.293 watt and is represented by the symbol Btu/h (not Btuh).

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