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inH2O - Inches of Water Column at 4 deg C Pressure Unit
Inches of water gauge or column is an english and american unit for measuring liquid level. 1 inch of water column at 4 degrees celsius equals 249.089 Pascals. The hydrostatic pressure generated by a certain liquid level is typically represented by the equivalent height of a water column. Since the pressure exerted by one inch of water is dependent on its density and the local gravity it is not a fundamental unit of measure for pressure but a derived one which is called a manometric unit.
Inches of water column or water gauge are used throughout the world for measuring shallow liquid level and low pressures such as differential air pressures in ventilation systems.
Since the density of a liquid is affected by changes in temperature, inches of water column should be accompanied by the temperature of the liquid that the units were derived. A pure water density of 1000 kg/m3 at 4 deg C and standard gravity of 9.80665 m/s2 is used in the calculation of this pressure unit. The significance of 4 degrees Celsius (39.2 degrees Fahrenheit) is that it is very close to the temperature that water reaches its maximum density.
It is conventional practise to use 1000 kg/m3 as the density of pure water at 4 deg C which is very close to the precise density and for most measurements this does not introduce any significant error. In fact since the temperature can vary significantly, measuring pressure in inches of water is never going to be a precise representation of the true liquid height. Local gravity also varies at different geological locations, which also adds some minor uncertainties to the use of inches of water gauge as an indication of exact water level in different parts of the world.
Use the following conversion factors to convert from inH2O to other pressure units or vica versa. To convert a reading in inH2O to another unit multiply it by the relevant pressure conversion factor. To convert a reading in any pressure unit to inH2O divide it by the relevant pressure conversion factor.
Alternatively convert from a inH2O pressure value into another unit using the pressure unit converter.
inH2O Pressure Conversion Factors
| 0.00249089 | bar |
| 0.0361273 | psi |
| 2.49089 | mbar |
| 249.089 | N/m² |
| 249.089 | Pa |
| 2.49089 | hPa |
| 0.249089 | kPa |
| 0.000249089 | MPa |
| 0.00254000 | kgf/cm² |
| 25.4 | mmH2O 4°C (39.2°F) |
| 2.54 | cmH2O 4°C (39.2°F) |
| 0.0254 | mH2O 4°C (39.2°F) |
| 0.0833333 | ftH2O 4°C (39.2°F) |
| 1.86832 | mmHg 0°C (32°F) |
| 0.186832 | cmHg 0°C (32°F) |
| 0.0735559 | inHg 0°C (32°F) |
| 1.86832 | Torr |
| 1868.32 | mtorr |
| 0.00245832 | atm |
| 2490.89 | Dynes/cm² |
| 0.578037 | oz/in² |
| 1868.32 | µHg 0°C |
| 0.0000161283 | tfsi (UK) |
| 0.0000180636 | tfsi (USA) |
| 0.00260117 | tfsf (USA) |
| 5.20233 | psf (USA) |
| 2.54 | gf/cm² |
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Site Last Updated: 14/05/08
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