British thermal unit

American  

noun

Physics.

1. the amount of heat required to raise the temperature of 1 pound (0.4 kilogram) of water 1°F. Btu, BTU, B.t.u., B.T.U., B.th.u.

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British thermal unit British  

noun

1. Abbrevs: btu.   BThU.  a unit of heat in the fps system equal to the quantity of heat required to raise the temperature of 1 pound of water by 1°F. 1 British thermal unit is equivalent to 1055.06 joules or 251.997 calories

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British thermal unit Scientific  

/ brĭt′ĭsh /

1. A unit used mainly to measure heat but also applied to other forms of energy. One British thermal unit is equal to the amount of heat needed to raise the temperature of one pound of water by one degree Fahrenheit, or 251.997 calories.

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British thermal unit Cultural  

1. A unit for measuring heat. One Btu raises the temperature of one pound of water one degree Fahrenheit (see also Fahrenheit).

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Etymology

Origin of British thermal unit

First recorded in 1875–80

Example Sentences

Meanwhile, U.S. futures on the New York Mercantile Exchange fall 7.1% to $3.183 per million British thermal unit.

From The Wall Street Journal • Feb. 9, 2026

Natural-gas futures touched $4.87 per British thermal unit in New York Jan. 24 before falling to a 15-week low of $3.73 per Btu on March 4.

From BusinessWeek • Mar. 9, 2011

Business people The initials B.T.U. stand for British thermal unit, the basic measurement of heat in a given amount of energy.

From Time Magazine Archive

The number of foot pounds of mechanical energy equivalent to one British thermal unit.

From Hawkins Electrical Guide, Number One Questions, Answers, & Illustrations, A Progressive Course of Study for Engineers, Electricians, Students and Those Desiring to acquire a Working Knowledge of Electricity and its Applications by Hawkins, Nehemiah

Heat-energy and mechanical energy are mutually convertible, one British thermal unit being the equivalent in heat-energy of 772 foot-pounds of mechanical energy, and one metric calorie equal to 423.55 kilogrammetres of work.

From A History of the Growth of the Steam-Engine by Thurston, Robert H.