British thermal unit

noun

: the quantity of heat required to raise the temperature of one pound of water one degree Fahrenheit at a specified temperature (such as 39°F)

Did you know?

Despite its name, the British thermal unit, or BTU, may be more widely used in North America than in Britain. Air conditioners, furnaces, and stoves are generally rated by BTUs. (Though "BTUs" is often short for "BTUs per hour;" in air-conditioner ratings, for instance, "BTUs" really means "BTUs of cooling capacity per hour".) Fuels such as natural gas and propane are also compared using BTUs. The BTU first appeared in 1865 and isn't part of the metric system—the metric unit of energy is the much smaller joule—so it isn't much used by scientists, but its practicality keeps it popular for consumer goods and fuels. A better-known heat unit is the calorie; a BTU is equal to about 252 calories. (Since the familiar food calorie is actually a kilocalorie, a BTU equals only about a quarter of a food calorie.)

Examples of British thermal unit in a Sentence

Recent Examples on the Web

That refers to a 1993 House vote on a controversial energy tax during the first year of Bill Clinton's presidency based on British thermal units. —Bart Jansen, USA Today, 8 June 2025

What to look for in a quality Char-Broil grill BTU British thermal units are a measure of heat performance that applies to gas grills. —Bestreviews, Chicago Tribune, 23 May 2025

According to the Energy Information Administration, renewables provided about 9%, or 8.2 quadrillion British thermal units, of total U.S. energy consumption in 2023. —Kurt Snibbe, Oc Register, 22 Apr. 2025

It’s measured in square inches and British thermal units, which relate to the amount of heat the grill can produce. —Bestreviews, Mercury News, 3 Apr. 2025

While tariffs could slightly increase U.S. natural gas prices, Goldman Sachs estimates the rise would be only a few cents per million British thermal units (MMBtu) above the current $4 level. —Dan Eberhart, Forbes, 19 Mar. 2025

Energy Transfer's Oasis Pipeline LP will provide as much as 450 billion British thermal units per day of natural gas to supply CloudBurst's data center campus outside of San Marcos, Texas, Energy Transfer said Monday in a statement. —arkansasonline.com, 11 Feb. 2025

Benchmark Henry Hub natural gas reached $3.66 per million British thermal units on Thursday, peaking at $4.20 earlier in the week. —Amanda Castro, Newsweek, 3 Jan. 2025

Word History

First Known Use

1865, in the meaning defined above

Rhymes for British thermal unit

• lunate
• multiunit
• subunit

Kids Definition

British thermal unit

noun

: the quantity of heat required to raise the temperature of one pound of water one degree Fahrenheit at a specified temperature (as 39°F or 60°F) and equal to about 1055 joules

—called also Btu

Medical Definition

British thermal unit

noun

: the quantity of heat required to raise the temperature of one pound of water one degree Fahrenheit at a specified temperature (as 39°F)

—abbreviation Btu