Convert Atmospheres to Millimeters of Water
1 atmosphere (atm) equals 10332.27453 millimeters of water (mmH₂O).
1 atm = 10332.27453 mmH₂O
Type in either box. Scientific notation works: 1.5e-3.
Converting a list? Use the bulk atmosphere to millimeter of water converter to paste a column from Excel.
How to Convert Atmosphere to Millimeter of Water
- 1 atm = 10332.27453 mmH₂O
- 1 mmH₂O = 0.00009678411054 atm
- Example: convert 15 atm to mmH₂O: 15 atm = 15 × 10332.27453 mmH₂O = 154984.1179 mmH₂O
Reference conditions. mmH₂O: Conventional water column: ρ = 1000 kg/m³ and gₙ = 9.80665 m/s² (≈ water at 4 °C).
Formula
mmH₂O = atm × 10332.274528
Derivation from SI units:
- 1 atm = 101 325 Pa (exact, by definition)
- 1 mmH₂O = 1000 kg/m³ × 9.80665 m/s² × 0.001 m = 9.80665 Pa
- 1 atm = 101325 Pa ÷ 9.80665 Pa per mmH₂O = 10332.274528 mmH₂O
Both units are defined exactly, so the factor is exact. Atmosphere definition: atmosphere; Millimeter of Water definition: millimeter of water.
Worked examples
- A reading of 1.5 atm converts to 15498.41179 mmH₂O.
1.5 atm × 10332.27453 = 15498.41179 mmH₂O - A value of 10 atm is 103322.7453 mmH₂O.
10 atm × 10332.27453 = 103322.7453 mmH₂O
Atmosphere to Millimeter of Water conversion table
| Atmospheres (atm) | Millimeters of Water (mmH₂O) |
|---|---|
| 0.001 atm | 10.33227453 mmH₂O |
| 0.01 atm | 103.3227453 mmH₂O |
| 0.1 atm | 1033.227453 mmH₂O |
| 0.25 atm | 2583.068632 mmH₂O |
| 0.5 atm | 5166.137264 mmH₂O |
| 1 atm | 10332.27453 mmH₂O |
| 1.5 atm | 15498.41179 mmH₂O |
| 2 atm | 20664.54906 mmH₂O |
| 2.5 atm | 25830.68632 mmH₂O |
| 3 atm | 30996.82358 mmH₂O |
| 4 atm | 41329.09811 mmH₂O |
| 5 atm | 51661.37264 mmH₂O |
| 10 atm | 103322.7453 mmH₂O |
| 20 atm | 206645.4906 mmH₂O |
| 50 atm | 516613.7264 mmH₂O |
| 100 atm | 1033227.453 mmH₂O |
| 200 atm | 2066454.906 mmH₂O |
| 300 atm | 3099682.358 mmH₂O |
| 1000 atm | 10332274.53 mmH₂O |
Where it's used
Atmospheres are used for chemistry and gas laws (STP and NTP conditions), 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.
Atmosphere to other pressure units
| Conversion | 1 atm equals |
|---|---|
| atmosphere to pascal | 101325 Pa |
| atmosphere to kilopascal | 101.325 kPa |
| atmosphere to megapascal | 0.101325 MPa |
| atmosphere to psi | 14.69594878 psi |
| atmosphere to bar | 1.01325 bar |
| atmosphere to millibar | 1013.25 mbar |
| atmosphere to decibar | 10.1325 dbar |
| atmosphere to torr | 760 Torr |
| atmosphere to millimeter of mercury | 759.9998917 mmHg |
| atmosphere to millimeter of water | 10332.27453 mmH₂O |
| atmosphere to centimeter of water | 1033.227453 cmH₂O |
| atmosphere to inch of water | 406.7824617 inH₂O |
| atmosphere to inch of water (60 °F) | 407.1893586 inH₂O (60 °F) |
| atmosphere to inch of mercury | 29.92125558 inHg |
| atmosphere to barye | 1013250 Ba |
Frequently asked questions
How many millimeters of water are in 1 atmosphere?
1 atm = 10332.27453 mmH₂O.
How do I convert atmospheres to millimeters of water?
Multiply the value in atm by 10332.27453. For example, 15 atm × 10332.27453 = 154984.1179 mmH₂O.
Is the atm 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, "atmosphere, standard (atm)".
- 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 Atmospheres to Millimeters of Water. Retrieved October 17, 2026, from https://scientificconverters.com/pressure/atmosphere-to-millimeter-of-water/
IEEE
Scientific Converters, "Convert Atmospheres to Millimeters of Water," scientificconverters.com. Accessed: Oct. 17, 2026. [Online]. Available: https://scientificconverters.com/pressure/atmosphere-to-millimeter-of-water/