Convert Millimeters of Water to psi (mmH2O to psi)
1 millimeter of water (mmH₂O) equals 0.001422334331 psi.
1 mmH₂O = 0.001422334331 psi
Type in either box. Scientific notation works: 1.5e-3.
Converting a list? Use the bulk millimeter of water to psi converter to paste a column from Excel.
How to Convert Millimeter of Water to psi
- 1 mmH₂O = 0.001422334331 psi
- 1 psi = 703.0695796 mmH₂O
- Example: convert 200 mmH₂O to psi: 200 mmH₂O = 200 × 0.001422334331 psi = 0.2844668661 psi
Reference conditions. mmH₂O: Conventional water column: ρ = 1000 kg/m³ and gₙ = 9.80665 m/s² (≈ water at 4 °C).
Formula
psi = mmH₂O × 0.001422334330712
or psi = mmH₂O ÷ 703.0695796392
Derivation from SI units:
- 1 mmH₂O = 1000 kg/m³ × 9.80665 m/s² × 0.001 m = 9.80665 Pa
- 1 psi = 1 lbf/in² = (0.45359237 kg × 9.80665 m/s²) ÷ (0.0254 m)² = 6894.757293168 Pa
- 1 mmH₂O = 9.80665 Pa ÷ 6894.757293168 Pa per psi = 0.001422334330712 psi
Both units are defined exactly, so the factor is exact. Millimeter of Water definition: millimeter of water; psi definition: psi.
Worked examples
- 1000 mmH₂O is 1.422334331 psi.
1000 mmH₂O × 0.001422334331 = 1.422334331 psi - A 200 mmH₂O blower pressure is 0.2844668661 psi.
200 mmH₂O × 0.001422334331 = 0.2844668661 psi
Millimeter of Water to psi conversion table
| Millimeters of Water (mmH₂O) | psi |
|---|---|
| 1 mmH₂O | 0.001422334331 psi |
| 2 mmH₂O | 0.002844668661 psi |
| 5 mmH₂O | 0.007111671654 psi |
| 10 mmH₂O | 0.01422334331 psi |
| 15 mmH₂O | 0.02133501496 psi |
| 20 mmH₂O | 0.02844668661 psi |
| 25 mmH₂O | 0.03555835827 psi |
| 30 mmH₂O | 0.04267002992 psi |
| 50 mmH₂O | 0.07111671654 psi |
| 75 mmH₂O | 0.1066750748 psi |
| 100 mmH₂O | 0.1422334331 psi |
| 150 mmH₂O | 0.2133501496 psi |
| 200 mmH₂O | 0.2844668661 psi |
| 250 mmH₂O | 0.3555835827 psi |
| 300 mmH₂O | 0.4267002992 psi |
| 500 mmH₂O | 0.7111671654 psi |
| 1000 mmH₂O | 1.422334331 psi |
| 2000 mmH₂O | 2.844668661 psi |
| 5000 mmH₂O | 7.111671654 psi |
| 10000 mmH₂O | 14.22334331 psi |
Where it's used
Water-column pressures in mmH₂O are converted to psi for US gauges and data sheets. 1 mmH₂O is about 0.001422 psi.
Millimeter of Water to other pressure units
| Conversion | 1 mmH₂O equals |
|---|---|
| millimeter of water to pascal | 9.80665 Pa |
| millimeter of water to kilopascal | 0.00980665 kPa |
| millimeter of water to megapascal | 0.00000980665 MPa |
| millimeter of water to psi | 0.001422334331 psi |
| millimeter of water to bar | 0.0000980665 bar |
| millimeter of water to millibar | 0.0980665 mbar |
| millimeter of water to decibar | 0.000980665 dbar |
| millimeter of water to torr | 0.07355592401 Torr |
| millimeter of water to millimeter of mercury | 0.07355591353 mmHg |
| millimeter of water to centimeter of water | 0.1 cmH₂O |
| millimeter of water to inch of water | 0.03937007874 inH₂O |
| millimeter of water to inch of water (60 °F) | 0.03940945989 inH₂O (60 °F) |
| millimeter of water to inch of mercury | 0.002895902107 inHg |
| millimeter of water to atmosphere | 0.00009678411054 atm |
| millimeter of water to barye | 98.0665 Ba |
Frequently asked questions
How many psi is 1000 mmH2O?
1000 mmH₂O = 1.422334331 psi.
How many psi are in 1 millimeter of water?
1 mmH₂O = 0.001422334331 psi.
How do I convert millimeters of water to psi?
Multiply the value in mmH₂O by 0.001422334331, or divide it by 703.0695796. For example, 200 mmH₂O × 0.001422334331 = 0.2844668661 psi.
Is the mmH₂O to psi conversion exact?
Yes. Both units are defined exactly, so the ratio is exact; its decimal form does not terminate and is shown here to 10 significant figures (more with the precision selector).
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, "millimeter of water, conventional (mmH2O)".
- 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, "pound-force per square inch (psi)".
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 Millimeters of Water to psi (mmH2O to psi). Retrieved October 18, 2026, from https://scientificconverters.com/pressure/millimeter-of-water-to-psi/
IEEE
Scientific Converters, "Convert Millimeters of Water to psi (mmH2O to psi)," scientificconverters.com. Accessed: Oct. 18, 2026. [Online]. Available: https://scientificconverters.com/pressure/millimeter-of-water-to-psi/