›› Measurement unit: in Hg

Full name: inch mercury [0 C]

Plural form: inches mercury

Symbol: in Hg

Alternate spelling: inches Hg

Category type: pressure

Scale factor: 3386.38866667

›› SI unit: pascal

The SI derived unit for pressure is the pascal.
1 pascal is equal to 0.000295299830714 in Hg.

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›› Definition: Inch mercury

Inches of mercury or inHg is a non-SI unit for pressure. It is still widely used for barometric pressure in weather reports and aviation in the United States, but is considered somewhat outdated elsewhere.

It is defined as the pressure exerted by a column of mercury of 1 inch in height at 32 F (0 C) at the standard acceleration of gravity.

1 inHg = 3,386.389 pascals at 0 C.

Aircraft operating at higher altitudes (above 18,000 feet) set their barometric altimeters to a standard pressure of 29.92 inHg or 1,013.2 hPa (1 hPa = 1 mbar) regardless of the actual sea level pressure, with inches of mercury used in the U.S. and Canada. The resulting altimeter readings are known as flight levels.

Piston engine aircraft with constant-speed propellers also use inHg to measure manifold pressure, which is indicative of engine power produced.

›› Sample conversions: in Hg

in Hg to hectopascal
in Hg to pound/square foot
in Hg to micropascal
in Hg to picopascal
in Hg to microbar
in Hg to foot water [4 C]
in Hg to femtopascal
in Hg to decipascal
in Hg to inch of water column
in Hg to megabar