# 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.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

## 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.