Millimeter of water

The millimeter of water (mmH2O or mm wg) is a unit of pressure frequently used in various applications, especially in situations where small pressure differences need to be accurately measured. It's often employed in fields ranging from meteorology to medical sciences.

Definition and Usage

The millimeter of water is defined as the pressure exerted by a column of water one millimeter in height at the standard acceleration due to gravity. It provides a way to express subtle pressure changes and is particularly useful in contexts where precision matters.

Applications in Different Fields

The millimeter of water is valuable in several domains:

  • Meteorology: It's used to measure and report atmospheric pressure.
  • Hydrology: Millimeter of water is used in studies related to water bodies and water pressures.
  • Medical Sciences: It's employed to measure pressure in bodily fluids.

Conversions and Equivalents

Understanding conversions of millimeters of water to other pressure units is essential:

  • 1 Millimeter of Water (mmH2O) = 9.80665 Pascal (Pa)
  • 1 Millimeter of Water (mmH2O) ≈ 0.980665 mbar
  • 1 Millimeter of Water (mmH2O) ≈ 0.000980665 bar
  • 1 Millimeter of Water (mmH2O) ≈ 0.014223 psi

Usage in Meteorology and Beyond

The millimeter of water is frequently encountered:

  • Meteorological Reports: It's used to describe atmospheric pressure conditions.
  • Fluid Pressure Measurement: A millimeter of water is applied in hydraulic systems.
  • Medical Instruments: It's used in devices that monitor bodily fluid pressures.


The millimeter of water (mmH2O) is a versatile unit of pressure utilized across various fields, from meteorology to medical sciences. Its ability to precisely measure small pressure differences makes it an essential tool in accurately assessing fluid pressures and atmospheric conditions.

Keywords: Millimeter of Water, mmH2O, pressure unit, meteorology, hydrology, medical sciences, conversions