Convert psi to Millimeters of Water
1 psi equals 703.0695796 millimeters of water (mmH₂O).
1 psi = 703.0695796 mmH₂O
Type in either box. Scientific notation works: 1.5e-3.
Converting a list? Use the bulk psi to millimeter of water converter to paste a column from Excel.
How to Convert psi to Millimeter of Water
- 1 psi = 703.0695796 mmH₂O
- 1 mmH₂O = 0.001422334331 psi
- Example: convert 15 psi to mmH₂O: 15 psi = 15 × 703.0695796 mmH₂O = 10546.04369 mmH₂O
Reference conditions. mmH₂O: Conventional water column: ρ = 1000 kg/m³ and gₙ = 9.80665 m/s² (≈ water at 4 °C).
Formula
mmH₂O = psi × 703.0695796392
Derivation from SI units:
- 1 psi = 1 lbf/in² = (0.45359237 kg × 9.80665 m/s²) ÷ (0.0254 m)² = 6894.757293168 Pa
- 1 mmH₂O = 1000 kg/m³ × 9.80665 m/s² × 0.001 m = 9.80665 Pa
- 1 psi = 6894.757293168 Pa ÷ 9.80665 Pa per mmH₂O = 703.0695796392 mmH₂O
Both units are defined exactly, so the factor is exact. psi definition: psi; Millimeter of Water definition: millimeter of water.
Worked examples
- A reading of 14.7 psi converts to 10335.12282 mmH₂O.
14.7 psi × 703.0695796 = 10335.12282 mmH₂O - A value of 60 psi is 42184.17478 mmH₂O.
60 psi × 703.0695796 = 42184.17478 mmH₂O
psi to Millimeter of Water conversion table
| psi | Millimeters of Water (mmH₂O) |
|---|---|
| 0.01 psi | 7.030695796 mmH₂O |
| 0.05 psi | 35.15347898 mmH₂O |
| 0.1 psi | 70.30695796 mmH₂O |
| 0.25 psi | 175.7673949 mmH₂O |
| 0.5 psi | 351.5347898 mmH₂O |
| 1 psi | 703.0695796 mmH₂O |
| 2 psi | 1406.139159 mmH₂O |
| 5 psi | 3515.347898 mmH₂O |
| 10 psi | 7030.695796 mmH₂O |
| 14.7 psi | 10335.12282 mmH₂O |
| 15 psi | 10546.04369 mmH₂O |
| 20 psi | 14061.39159 mmH₂O |
| 25 psi | 17576.73949 mmH₂O |
| 30 psi | 21092.08739 mmH₂O |
| 32 psi | 22498.22655 mmH₂O |
| 35 psi | 24607.43529 mmH₂O |
| 40 psi | 28122.78319 mmH₂O |
| 50 psi | 35153.47898 mmH₂O |
| 60 psi | 42184.17478 mmH₂O |
| 80 psi | 56245.56637 mmH₂O |
| 100 psi | 70306.95796 mmH₂O |
| 125 psi | 87883.69745 mmH₂O |
| 150 psi | 105460.4369 mmH₂O |
| 200 psi | 140613.9159 mmH₂O |
| 500 psi | 351534.7898 mmH₂O |
| 1000 psi | 703069.5796 mmH₂O |
| 3000 psi | 2109208.739 mmH₂O |
| 5000 psi | 3515347.898 mmH₂O |
Where it's used
psi are used for tyre pressure in the United States (about 30–35 psi for cars), while millimeters of water appear in fan static pressure and duct design in Asia and Europe. Both measure pressure, stress and differential pressure (force per unit area), so the conversion is a fixed factor.
psi to other pressure units
| Conversion | 1 psi equals |
|---|---|
| psi to pascal | 6894.757293 Pa |
| psi to kilopascal | 6.894757293 kPa |
| psi to megapascal | 0.006894757293 MPa |
| psi to bar | 0.06894757293 bar |
| psi to millibar | 68.94757293 mbar |
| psi to decibar | 0.6894757293 dbar |
| psi to torr | 51.71493257 Torr |
| psi to millimeter of mercury | 51.7149252 mmHg |
| psi to millimeter of water | 703.0695796 mmH₂O |
| psi to centimeter of water | 70.30695796 cmH₂O |
| psi to inch of water | 27.67990471 inH₂O |
| psi to inch of water (60 °F) | 27.7075924 inH₂O (60 °F) |
| psi to inch of mercury | 2.036020677 inHg |
| psi to atmosphere | 0.06804596391 atm |
| psi to barye | 68947.57293 Ba |
Frequently asked questions
How many millimeters of water are in 1 psi?
1 psi = 703.0695796 mmH₂O.
How do I convert psi to millimeters of water?
Multiply the value in psi by 703.0695796. For example, 15 psi × 703.0695796 = 10546.04369 mmH₂O.
Is the psi to mmH₂O 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, "pound-force per square inch (psi)".
- 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)".
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 psi to Millimeters of Water. Retrieved October 17, 2026, from https://scientificconverters.com/pressure/psi-to-millimeter-of-water/
IEEE
Scientific Converters, "Convert psi to Millimeters of Water," scientificconverters.com. Accessed: Oct. 17, 2026. [Online]. Available: https://scientificconverters.com/pressure/psi-to-millimeter-of-water/