›› Measurement unit: inch mercury

Full name:

Plural form: inches mercury

Symbol: in Hg

Alternate spelling: inches Hg

Category type: pressure

Scale factor: 3386.389

›› SI unit: pascal

The SI derived unit for pressure is the pascal.
1 pascal is equal to 0.00029529980164712 inch mercury.

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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widely used for barometric pressure in weather reports and aviation in the United States, but is considered somewhat outdated elsewhere.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: inch mercury

inch mercury to petapascal
inch mercury to zeptopascal
inch mercury to terabar
inch mercury to decitorr
inch mercury to terapascal
inch mercury to zettabar
inch mercury to foot mercury [0 °C]
inch mercury to kilogram-force/square millimetre
inch mercury to ton/square inch [short]
inch mercury to picopascal