Millimeters, water gauge
Millimeters, water gauge, also known as a millimetre of water or millimetres water column and abbreviated to mmwg, mmH2O or mmwc, respectively, is a less commonly used unit of pressure. It may be defined as the pressure exerted by a column of water of 1 mm in height at 4 °C at the standard acceleration of gravity, so that = × × 1 mm = ≈, but conventionally a nominal maximum water density of is used, giving.
In limited and largely historic contexts it may vary with temperature, using the equation:
The unit is often used to describe how much water rainwear or other outerwear can take or how much water a tent can resist without leaking.
