Inch of water

The inch of water (inH2O, iwg or in.w.g., inch wc, in. WC, " wc, etc. or just wc or WC), inAq, Aq) is a unit of pressure frequently used to measure small pressure differences in various applications. It's particularly useful in fields like HVAC (Heating, Ventilation, and Air Conditioning) and fluid dynamics, where accurate pressure measurements are crucial.

Definition and Usage

The inch of water is defined as the pressure exerted by a column of water one inch in height at the standard acceleration due to gravity. This unit provides a practical way to measure and discuss low-pressure conditions in fluid systems.

Applications in Engineering and HVAC

The inch of water finds its applications in multiple areas:

  • HVAC Systems: It's used to measure and adjust air pressure in ventilation systems.
  • Fluid Engineering: Engineers use inch of water to analyze and optimize fluid flows.
  • Medical Devices: It's applied in devices measuring air pressure in respiratory systems.

Conversions and Equivalents

Understanding conversions of inch of water to other pressure units is important:

  • 1 Inch of Water (inH2O) = 248.84 Pascal (Pa)
  • 1 Inch of Water (inH2O) ≈ 2.4884 mbar
  • 1 Inch of Water (inH2O) ≈ 0.0024884 bar
  • 1 Inch of Water (inH2O) ≈ 0.03613 psi

Usage in HVAC and Engineering

The inch of water is widely used in different fields:

  • Airflow Analysis: Engineers use inch of water to optimize air and fluid flow systems.
  • Building Pressure Control: It's used in maintaining balanced air pressure in buildings.
  • Respiratory Equipment: Inch of water is applied in devices measuring lung pressure.


The inch of water (inH2O) is a vital unit of pressure in engineering, HVAC, and medical fields. Its ability to measure small pressure differences accurately makes it an essential tool for maintaining optimal fluid flows, ensuring building comfort and assessing respiratory health.

Keywords: Inch of Water, inH2O, pressure unit, HVAC, fluid engineering, conversions