›› Convert to inch of mercury [0 °C]

millimeter mercury
inch of mercury

›› More information from the unit converter

How many millimeter mercury in 1 inch of mercury? The answer is 25.400000197459.
We assume you are converting between and inch of mercury [0 °C].
You can view more details on each measurement unit:
millimeter mercury or inch of mercury
The SI derived unit for pressure is the pascal.
1 pascal is equal to 0.0075006157584566 millimeter mercury, or 0.00029529983071445 inch of 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 of mercury.
Type in your own numbers in the form to convert the units!

›› Quick conversion chart of millimeter mercury to inch of mercury

1 millimeter mercury to inch of mercury = 0.03937 inch of mercury

10 millimeter mercury to inch of mercury = 0.3937 inch of mercury

20 millimeter mercury to inch of mercury = 0.7874 inch of mercury

30 millimeter mercury to inch of mercury = 1.1811 inch of mercury

40 millimeter mercury to inch of mercury = 1.5748 inch of mercury

50 millimeter mercury to inch of mercury = 1.9685 inch of mercury

100 millimeter mercury to inch of mercury = 3.93701 inch of mercury

200 millimeter mercury to inch of mercury = 7.87402 inch of mercury

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You can do the reverse unit conversion from inch of mercury to millimeter mercury, or enter any two units below:

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›› Common pressure conversions

millimeter mercury to bar
millimeter mercury to atmosphere
millimeter mercury to water column
millimeter mercury to millimeter of water
millimeter mercury to inch of water
millimeter mercury to ton/square meter
millimeter mercury to kilopond/square centimeter
millimeter mercury to centitorr
millimeter mercury to kilobar
millimeter mercury to micron of mercury

›› 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 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.

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