Millimeter of Water

millimeter of water [′mil·ə‚mēd·ər əv ′wȯdər]

(mechanics)

A unit of pressure, equal to the pressure exerted by a column of water 1 millimeter high with a density of 1 gram per cubic centimeter under the standard acceleration of gravity; equal to 9.80665 pascals. Abbreviated mmH₂O.

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Millimeter of Water 

a subsidiary unit of pressure that is used in many fields of technology (mainly in hydraulics). The notations are as follows: Russian, mm vod. St.; international, mm HiO. A millimeter of water is equal to the hydrostatic pressure of a column of water 1 mm high at its highest density (that is, at a temperature of about 4°C) and a gravitational acceleration g = 9.80665 m/sec². The relationships between the millimeter of water and other units of pressure are as follows: 1 mm H₂O = 9.80665 newtons per sq m = 10⁻⁴ kilogram-force per sq cm = 7.3556 × 10⁻² mm Hg.