›› 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.


›› Convert inch mercury to another unit

Convert inch mercury to  

Valid units must be of the pressure type.
You can use this form to select from known units:

Convert inch mercury to  


›› 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widely used for barometric pressure in weather reports and aviation in the United States, but is considered somewhat outdated elsewhere.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 technical atmosphere
inch mercury to pound/square inch [gauge]
inch mercury to micrometer of mercury [0 C]
inch mercury to meter of air [15 C]
inch mercury to kilopond/square centimetre
inch mercury to centimeter of water [4 C]
inch mercury to foot water [4 C]
inch mercury to ton/square foot [long]
inch mercury to foot of air [15 C]
inch mercury to kilogram-force/square metre