How many inch of mercury in 1 mm H2O?
The answer is 0.0028959020848759.

We assume you are converting between **inch of mercury [0 °C]** and **millimeter water [4 °C]**.

You can view more details on each measurement unit:

inch of mercury or
mm H2O

The SI derived unit for **pressure** is the pascal.

1 pascal is equal to 0.00029529983071445 inch of mercury, or 0.10197162129779 mm H2O.

Note that rounding errors may occur, so always check the results.

Use this page to learn how to convert between inches of mercury and millimeters water.

Type in your own numbers in the form to convert the units!

1 inch of mercury to mm H2O = 345.31554 mm H2O

2 inch of mercury to mm H2O = 690.63109 mm H2O

3 inch of mercury to mm H2O = 1035.94663 mm H2O

4 inch of mercury to mm H2O = 1381.26217 mm H2O

5 inch of mercury to mm H2O = 1726.57771 mm H2O

6 inch of mercury to mm H2O = 2071.89326 mm H2O

7 inch of mercury to mm H2O = 2417.2088 mm H2O

8 inch of mercury to mm H2O = 2762.52434 mm H2O

9 inch of mercury to mm H2O = 3107.83988 mm H2O

10 inch of mercury to mm H2O = 3453.15543 mm H2O

You can do the reverse unit conversion from mm H2O to inch of mercury, or enter any two units below:

inch of mercury to terapascal

inch of mercury to pieze

inch of mercury to inch of water

inch of mercury to hectobar

inch of mercury to zeptopascal

inch of mercury to megapascal

inch of mercury to centimeter mercury

inch of mercury to kilopond/square meter

inch of mercury to poundal/square foot

inch of mercury to centimeter 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widely used for barometric pressure in weather reports and aviation in the United States, but is considered somewhat outdated elsewhere.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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