- published: 17 Jun 2016
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The bar is a unit of pressure defined as 1,000,000 dynes per square centimetre (or equivalently in SI units, 100 kilopascals, or in CGS units, 1 megabarye). It is about equal to the atmospheric pressure on Earth at sea level.
Other units derived from the bar are the megabar (symbol: Mbar), kilobar (symbol: kbar), decibar (symbol: dbar), centibar (symbol: cbar), and millibar (symbol: mbar or mb). They are not SI units, nor are they cgs units, but they are accepted for use with the SI. The bar is widely used in descriptions of pressure because it is only about 1% smaller than the atmosphere (symbol: atm), which now is defined to be 1.01325 bar exactly. The bar is legally recognized in countries of the European Union.
In 1985 the IUPAC recommended that the standard for atmospheric pressure should be harmonized to 100,000 Pa = 1 bar = 750 Torr. The same definition is used in the compressor and the pneumatic tool industries (ISO 2787).
The bar and the millibar were introduced by the British meteorologist William Napier Shaw in 1909. He was the director of the Meteorological Office in London from 1907 to 1920.
Bar may refer to:
Unit may refer to: