Plural form: inches mercury
Symbol: in Hg
Alternate spelling: inches Hg
Category type: pressure
Scale factor: 3386.389
The SI derived unit for pressure is the pascal.
1 pascal is equal to 0.00029529980164712 inch mercury.
Valid units must be of the pressure type.
You can use this form to select from known units:
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widely used for barometric pressure in weather reports and aviation in the United States, but is considered somewhat outdated elsewhere.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.
inch mercury to foot of mercury [0 °C]
inch mercury to kilopascal
inch mercury to micrometer of mercury [0 °C]
inch mercury to millipascal
inch mercury to meganewton/square metre
inch mercury to ton/square foot [long]
inch mercury to foot of water [4 °C]
inch mercury to ton/square foot [short]
inch mercury to millihg
inch mercury to millimeter of water [4 °C]