Convert Inches of Water to Pascals
1 inch of water (inH₂O) equals 249.08891 pascals (Pa).
1 inH₂O = 249.08891 Pa
Type in either box. Scientific notation works: 1.5e-3.
Converting a list? Use the bulk inch of water to pascal converter to paste a column from Excel.
How to Convert Inch of Water to Pascal
- 1 inH₂O = 249.08891 Pa
- 1 Pa = 0.00401463076 inH₂O
- Example: convert 15 inH₂O to Pa: 15 inH₂O = 15 × 249.08891 Pa = 3736.33365 Pa
Reference conditions. inH₂O: Conventional water column: ρ = 1000 kg/m³ and gₙ = 9.80665 m/s² (≈ water at 4 °C).
Formula
Pa = inH₂O × 249.08891
Derivation from SI units:
- 1 inH₂O = 1000 kg/m³ × 9.80665 m/s² × 0.0254 m = 249.08891 Pa
- 1 Pa = 1 N/m² = 1 kg·m⁻¹·s⁻²
Both units are defined exactly, so the factor is exact. Inch of Water definition: inch of water; Pascal definition: pascal.
Worked examples
- A residential air handler rated for 0.5 inH₂O of external static pressure works against 124.544455 Pa.
0.5 inH₂O × 249.08891 = 124.544455 Pa - Many HVAC filters are due for replacement at about 1 inH₂O of pressure drop, which is 249.08891 Pa.
1 inH₂O × 249.08891 = 249.08891 Pa
Inch of Water to Pascal conversion table
| Inches of Water (inH₂O) | Pascals (Pa) |
|---|---|
| 0.01 inH₂O | 2.4908891 Pa |
| 0.02 inH₂O | 4.9817782 Pa |
| 0.03 inH₂O | 7.4726673 Pa |
| 0.05 inH₂O | 12.4544455 Pa |
| 0.1 inH₂O | 24.908891 Pa |
| 0.15 inH₂O | 37.3633365 Pa |
| 0.2 inH₂O | 49.817782 Pa |
| 0.25 inH₂O | 62.2722275 Pa |
| 0.3 inH₂O | 74.726673 Pa |
| 0.4 inH₂O | 99.635564 Pa |
| 0.5 inH₂O | 124.544455 Pa |
| 0.75 inH₂O | 186.8166825 Pa |
| 1 inH₂O | 249.08891 Pa |
| 1.5 inH₂O | 373.633365 Pa |
| 2 inH₂O | 498.17782 Pa |
| 2.5 inH₂O | 622.722275 Pa |
| 3 inH₂O | 747.26673 Pa |
| 4 inH₂O | 996.35564 Pa |
| 5 inH₂O | 1245.44455 Pa |
| 7 inH₂O | 1743.62237 Pa |
| 10 inH₂O | 2490.8891 Pa |
| 11 inH₂O | 2739.97801 Pa |
| 14 inH₂O | 3487.24474 Pa |
| 20 inH₂O | 4981.7782 Pa |
| 27.7 inH₂O | 6899.762807 Pa |
Where it's used
US HVAC drawings, test-and-balance reports and gas appliance labels use inches of water. Converting to pascals makes the numbers usable with SI fan curves, ISO 16890 filter data and cleanroom standards such as ISO 14644.
Inch of Water to other pressure units
| Conversion | 1 inH₂O equals |
|---|---|
| inch of water to pascal | 249.08891 Pa |
| inch of water to kilopascal | 0.24908891 kPa |
| inch of water to megapascal | 0.00024908891 MPa |
| inch of water to psi | 0.036127292 psi |
| inch of water to bar | 0.0024908891 bar |
| inch of water to millibar | 2.4908891 mbar |
| inch of water to decibar | 0.024908891 dbar |
| inch of water to torr | 1.86832047 Torr |
| inch of water to millimeter of mercury | 1.868320204 mmHg |
| inch of water to millimeter of water | 25.4 mmH₂O |
| inch of water to centimeter of water | 2.54 cmH₂O |
| inch of water to inch of water (60 °F) | 1.001000281 inH₂O (60 °F) |
| inch of water to inch of mercury | 0.07355591353 inHg |
| inch of water to atmosphere | 0.002458316408 atm |
| inch of water to barye | 2490.8891 Ba |
Frequently asked questions
What is 0.05 in WC in pascals?
0.05 inH₂O is 12.45 Pa, inside the 5–20 Pa range commonly used between adjacent cleanroom zones.
How many pascals are in 1 inch of water?
1 inH₂O = 249.08891 Pa.
How do I convert inches of water to pascals?
Multiply the value in inH₂O by 249.08891. For example, 15 inH₂O × 249.08891 = 3736.33365 Pa.
Is the inH₂O to Pa conversion exact?
Yes. Both units are defined exactly, and 1 inH₂O is exactly 249.08891 Pa.
Sources
- Guide for the Use of the International System of Units (SI), NIST Special Publication 811, 2008 Edition, National Institute of Standards and Technology , Appendix B.8, "inch of water, conventional (inH2O)".
- The International System of Units (SI), 9th edition (SI Brochure), Bureau International des Poids et Mesures , Table 4, coherent derived units with special names.
Last reviewed: . Factors are stored exactly and computed with 50-digit decimal arithmetic. See how we verify conversion factors.
Cite this page
APA
Scientific Converters. (2026, October 15). Convert Inches of Water to Pascals. Retrieved October 17, 2026, from https://scientificconverters.com/pressure/inch-of-water-to-pascal/
IEEE
Scientific Converters, "Convert Inches of Water to Pascals," scientificconverters.com. Accessed: Oct. 17, 2026. [Online]. Available: https://scientificconverters.com/pressure/inch-of-water-to-pascal/