Convert Inches of Water to Kilopascals (inH2O to kPa)
1 inch of water (inH₂O) equals 0.24908891 kilopascals (kPa).
1 inH₂O = 0.24908891 kPa
Type in either box. Scientific notation works: 1.5e-3.
Converting a list? Use the bulk inch of water to kilopascal converter to paste a column from Excel.
How to Convert Inch of Water to Kilopascal
- 1 inH₂O = 0.24908891 kPa
- 1 kPa = 4.01463076 inH₂O
- Example: convert 15 inH₂O to kPa: 15 inH₂O = 15 × 0.24908891 kPa = 3.73633365 kPa
Reference conditions. inH₂O: Conventional water column: ρ = 1000 kg/m³ and gₙ = 9.80665 m/s² (≈ water at 4 °C).
Formula
kPa = inH₂O × 0.24908891
or kPa = inH₂O ÷ 4.014630759756
Derivation from SI units:
- 1 inH₂O = 1000 kg/m³ × 9.80665 m/s² × 0.0254 m = 249.08891 Pa
- 1 kPa = 10³ Pa
- 1 inH₂O = 249.08891 Pa ÷ 1000 Pa per kPa = 0.24908891 kPa
Both units are defined exactly, so the factor is exact. Inch of Water definition: inch of water; Kilopascal definition: kilopascal.
Worked examples
- A natural-gas appliance supplied at 7 inH₂O is at 1.74362237 kPa.
7 inH₂O × 0.24908891 = 1.74362237 kPa - Propane appliances are typically supplied at 11 inH₂O, which is 2.73997801 kPa.
11 inH₂O × 0.24908891 = 2.73997801 kPa
Inch of Water to Kilopascal conversion table
| Inches of Water (inH₂O) | Kilopascals (kPa) |
|---|---|
| 0.01 inH₂O | 0.0024908891 kPa |
| 0.02 inH₂O | 0.0049817782 kPa |
| 0.03 inH₂O | 0.0074726673 kPa |
| 0.05 inH₂O | 0.0124544455 kPa |
| 0.1 inH₂O | 0.024908891 kPa |
| 0.15 inH₂O | 0.0373633365 kPa |
| 0.2 inH₂O | 0.049817782 kPa |
| 0.25 inH₂O | 0.0622722275 kPa |
| 0.3 inH₂O | 0.074726673 kPa |
| 0.4 inH₂O | 0.099635564 kPa |
| 0.5 inH₂O | 0.124544455 kPa |
| 0.75 inH₂O | 0.1868166825 kPa |
| 1 inH₂O | 0.24908891 kPa |
| 1.5 inH₂O | 0.373633365 kPa |
| 2 inH₂O | 0.49817782 kPa |
| 2.5 inH₂O | 0.622722275 kPa |
| 3 inH₂O | 0.74726673 kPa |
| 4 inH₂O | 0.99635564 kPa |
| 5 inH₂O | 1.24544455 kPa |
| 7 inH₂O | 1.74362237 kPa |
| 10 inH₂O | 2.4908891 kPa |
| 11 inH₂O | 2.73997801 kPa |
| 14 inH₂O | 3.48724474 kPa |
| 20 inH₂O | 4.9817782 kPa |
| 27.7 inH₂O | 6.899762807 kPa |
Where it's used
US gas and HVAC specifications in inches of water are converted to kPa for Canadian, Australian and international codes and for SI-based calculations.
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 7 in WC in kPa?
7 inH₂O = 1.744 kPa, the usual natural-gas supply pressure to appliances in North America.
How many kilopascals are in 1 inch of water?
1 inH₂O = 0.24908891 kPa.
How do I convert inches of water to kilopascals?
Multiply the value in inH₂O by 0.24908891, or divide it by 4.01463076. For example, 15 inH₂O × 0.24908891 = 3.73633365 kPa.
Is the inH₂O to kPa conversion exact?
Yes. Both units are defined exactly, and 1 inH₂O is exactly 0.24908891 kPa.
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 7, SI prefixes.
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 Kilopascals (inH2O to kPa). Retrieved October 18, 2026, from https://scientificconverters.com/pressure/inch-of-water-to-kilopascal/
IEEE
Scientific Converters, "Convert Inches of Water to Kilopascals (inH2O to kPa)," scientificconverters.com. Accessed: Oct. 18, 2026. [Online]. Available: https://scientificconverters.com/pressure/inch-of-water-to-kilopascal/