Inches Of Water to Pascals (inH₂O to Pa)
1 inch of water equals 249.08891 pascals exactly.
How to convert inches of water to pascals
To convert inches of water to pascals, multiply the number of inches of water by 249.08891. This factor is exact. To go the other way, multiply pascals by 0.00401463076 (rounded).
pascals = inches of water × 249.08891
Example: 10 inches of water = 2,490.8891 pascals.
About these units
Inch Of Water (inH₂O)
About 249.089 pascals (the conventional value, 25.4 mm × 9.80665 Pa). Used for air pressure in HVAC and gas appliances.
Building services and gas fitting rely on this unit. Manometers filled with water read small differences in air or gas pressure, and in North America the result is stated in inches of water column. Natural gas supplied to appliances is typically 6 to 7 inches WC, and HVAC technicians use it for pressure across coils, filters and ducts. A pipe organ's wind pressure is quoted the same way.
Which water is meant matters a little. Wikipedia gives about 249.082 Pa for water at 4 degrees Celsius, equal to 39.2 degrees Fahrenheit, and also the conventional 249.08891 Pa, which is 25.4 mm times 9.80665 and is the figure used here. NIST lists 249.082 Pa at 39.2 degrees Fahrenheit and 248.84 Pa at 60 degrees Fahrenheit, and some industry standards use 60 or 68 degrees Fahrenheit. About 27.7 inches of water equal 1 psi.
1 inch of water = 249.08891 pascals (exactly).
Sources: Wikipedia: Inch of water; NIST SP 811, Appendix B.8
Pascal (Pa)
The SI unit of pressure: one newton per square meter. A very small unit; atmospheric pressure is about 101,325 Pa.
Blaise Pascal never saw a pascal, because the name was adopted by the 14th CGPM in 1971 for the newton per square meter. He did, however, earn the honor. In 1647 he published experiments on the vacuum, and on 19 September 1648 his brother-in-law Florin Périer carried a mercury barometer up the Puy de Dôme near Clermont, where the column stood at about 23 inches against about 26 at the base. Pascal had reasoned that air pressure should fall with altitude, and the result confirmed it.
One pascal is a tiny pressure, so the unit is mostly met with prefixes. Standard atmospheric pressure is 101,325 Pa, a typical sea-level reading is about 1,013 hPa, and the threshold of hearing in air is taken as a reference pressure of 20 micropascals. Building airtightness tests, in contrast, are run at 50 Pa.
Pascal is also remembered for hydrostatics, where he showed that pressure depends on height difference rather than the weight of the fluid, and for the hydraulic press.
The pascal is the reference unit for pressure on this site.
Sources: Wikipedia: Pascal (unit); Wikipedia: Blaise Pascal
Related conversions
- Pascals to inches of water (reverse)
- Inches of water to kilopascals
- Inches of water to bars
- Inches of water to standard atmospheres
- Inches of water to PSI
- Kilopascals to pascals
- Bars to pascals
- Standard atmospheres to pascals
- PSI to pascals
- Hectopascals to pascals
- Megapascals to pascals
- Millibars to pascals
- Torr to pascals
- Millimeters of mercury to pascals
- Inches of mercury to pascals
- Gigapascals to pascals
- Kilopounds per square inch to pascals
See all pressure units.