Bar (unit)

The bar (symbol bar), decibar (symbol dbar) and the millibar (symbol mbar, also mb) are units of pressure. They are not SI units, but they are still used in descriptions of pressure. Although the use of those units is discouraged, the bar is about the same as atmospheric pressure.

Terms

The bar, the decibar, and the millibar are known as:

• 1 bar = 100,000 pascals (Pa) = 1,000,000 dynes per square centimeter (baryes)
• 1 dbar = 0.1 bar = 10,000 Pa = 100,000 dyn/cm²
• 1 mbar = 0.001 bar = 100 Pa = 1,000 dyn/cm²

(A pascal is one newton per square meter.)

Origin

The word bar has its origin in the Greek word βάρος (baros), meaning weight. Its official symbol is "bar"; the earlier "b" is no longer used but is still often seen especially as "mb," rather than the correct "mbar" for millibars.

The bar and the millibar were defined by Sir Napier Shaw in 1909 and became used internationally in 1929.

Bar (unit) Media

• 

  Map showing atmospheric pressure in mbar or hPa

• 

  A tire-pressure gauge displaying bar (outside) and pounds per square inch (inside)

Other websites

• Official SI website: Table 8. Non-SI units accepted for use with the SI Archived 2008-08-21 at the Wayback Machine
• Conversion factors from bar to various pressure units