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How many millimeter mercury in 1 inch mercury? The answer is 25.400002697664.
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You can view more details on each measurement unit:
millimeter mercury or inch mercury
The SI derived unit for pressure is the pascal.
1 pascal is equal to 0.0075006157584566 millimeter mercury, or 0.00029529980164712 inch mercury.
Note that rounding errors may occur, so always check the results.
Use this page to learn how to convert between millimeters mercury and inches mercury.
Type in your own numbers in the form to convert the units!


›› Quick conversion chart of millimeter mercury to inch mercury

1 millimeter mercury to inch mercury = 0.03937 inch mercury

10 millimeter mercury to inch mercury = 0.3937 inch mercury

20 millimeter mercury to inch mercury = 0.7874 inch mercury

30 millimeter mercury to inch mercury = 1.1811 inch mercury

40 millimeter mercury to inch mercury = 1.5748 inch mercury

50 millimeter mercury to inch mercury = 1.9685 inch mercury

100 millimeter mercury to inch mercury = 3.93701 inch mercury

200 millimeter mercury to inch mercury = 7.87401 inch mercury


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›› Common pressure conversions

millimeter mercury to zeptopascal
millimeter mercury to sthene/square meter
millimeter mercury to foot of water
millimeter mercury to hectobar
millimeter mercury to attobar
millimeter mercury to millihg
millimeter mercury to centimeter water
millimeter mercury to nanobar
millimeter mercury to centibar
millimeter mercury to centipascal


›› Definition: Millimeter mercury

The millimeter of mercury by definition is 133.322387415 Pa (13.5951 g/cm3 9.80665 m/s2 1 mm), which is approximated with known accuracies of density of mercury and standard gravity.

The torr is defined as 1/760 of one standard atmosphere, while the atmosphere is defined as 101325 pascals. Therefore, 1 Torr is equal to
101325/760 Pa. The decimal form of this fraction is approximately 133.322368421.

The relationship between the torr and the millimeter of mercury is:

1 Torr = 0.999999857533699 mmHg
1 mmHg = 1.000000142466321 Torr

The difference between one millimeter of mercury and one torr, as well as between one atmosphere (101.325 kPa) and 760 mmHg (101.3250144354 kPa), is less than one part in seven million (or less than 0.000015%). This small difference is negligible for most applications outside metrology.


›› 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.


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ConvertUnits.com provides an online conversion calculator for all types of measurement units. You can find metric conversion tables for SI units, as well as English units, currency, and other data. Type in unit symbols, abbreviations, or full names for units of length, area, mass, pressure, and other types. Examples include mm, inch, 100 kg, US fluid ounce, 6'3", 10 stone 4, cubic cm, metres squared, grams, moles, feet per second, and many more!