›› Measurement unit: inch of mercury

Full name: inch of mercury [0 C]

Plural form: inches of mercury

Symbol: inHg

Alternate spelling: inch Hg

Category type: pressure

Scale factor: 3386.3886666667


›› SI unit: pascal

The SI derived unit for pressure is the pascal.
1 pascal is equal to 0.00029529983071445 inch of mercury.


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widely used for barometric pressure in weather reports and aviation in the United States, but is considered somewhat outdated elsewhere.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

inch of mercury to inch water [4 C]
inch of mercury to hectobar
inch of mercury to pascal
inch of mercury to atmosphere [technical]
inch of mercury to attobar
inch of mercury to newton/square millimetre
inch of mercury to kilobar
inch of mercury to meter of air [15 C]
inch of mercury to millitorr
inch of mercury to decibar