# ››Convert pound/square inch to millimeter of water [4 °C]

 psi mmH2O

The above form works if you are measuring differential pressure, such as the difference in psi between two points. It also gives the correct answer for absolute pressure, assuming you are measuring psia, which is the pressure relative to absolute zero vacuum.

If you are measuring relative to vacuum and want to resolve the pressure relative to the atmosphere, then you should use the form below.

psi (relative to atmosphere)
mmH2O (relative to vacuum)

How many psi in 1 mmH2O? The answer is 0.0014223343334285.
We assume you are converting between pound/square inch and millimeter of water [4 °C].
You can view more details on each measurement unit:
psi or mmH2O
The SI derived unit for pressure is the pascal.
1 pascal is equal to 0.00014503773800722 psi, or 0.10197162129779 mmH2O.
Note that rounding errors may occur, so always check the results.
Use this page to learn how to convert between pounds/square inch and millimeters of water.
Type in your own numbers in the form to convert the units!

# ››Want other units?

You can do the reverse unit conversion from mmH2O to psi, or enter any two units below:

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# ››Definition: Pound/square inch

The pound per square inch or, more accurately, pound-force per square inch (symbol: psi or lbf/inē or lbf/inē) is a unit of pressure or of stress based on avoirdupois units. It is the pressure resulting from a force of one pound-force applied to an area of one square inch.

# ››Metric conversions and more

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!