Convert Millimeters of Water to Millimeters of Mercury
1 millimeter of water (mmH₂O) equals 0.07355591353 millimeters of mercury (mmHg).
1 mmH₂O = 0.07355591353 mmHg
Type in either box. Scientific notation works: 1.5e-3.
Converting a list? Use the bulk millimeter of water to millimeter of mercury converter to paste a column from Excel.
How to Convert Millimeter of Water to Millimeter of Mercury
- 1 mmH₂O = 0.07355591353 mmHg
- 1 mmHg = 13.5951 mmH₂O
- Example: convert 15 mmH₂O to mmHg: 15 mmH₂O = 15 × 0.07355591353 mmHg = 1.103338703 mmHg
Reference conditions. mmH₂O: Conventional water column: ρ = 1000 kg/m³ and gₙ = 9.80665 m/s² (≈ water at 4 °C). mmHg: Conventional mercury column: ρ = 13 595.1 kg/m³ and gₙ = 9.80665 m/s² (≈ mercury at 0 °C / 32 °F).
Formula
mmHg = mmH₂O × 0.07355591352767
or mmHg = mmH₂O ÷ 13.5951
Derivation from SI units:
- 1 mmH₂O = 1000 kg/m³ × 9.80665 m/s² × 0.001 m = 9.80665 Pa
- 1 mmHg = 13 595.1 kg/m³ × 9.80665 m/s² × 0.001 m = 133.322387415 Pa
- 1 mmH₂O = 9.80665 Pa ÷ 133.322387415 Pa per mmHg = 0.07355591352767 mmHg
Both units are defined exactly, so the factor is exact. Millimeter of Water definition: millimeter of water; Millimeter of Mercury definition: millimeter of mercury.
Worked examples
- A reading of 25 mmH₂O converts to 1.838897838 mmHg.
25 mmH₂O × 0.07355591353 = 1.838897838 mmHg - A value of 250 mmH₂O is 18.38897838 mmHg.
250 mmH₂O × 0.07355591353 = 18.38897838 mmHg
Millimeter of Water to Millimeter of Mercury conversion table
| Millimeters of Water (mmH₂O) | Millimeters of Mercury (mmHg) |
|---|---|
| 1 mmH₂O | 0.07355591353 mmHg |
| 2 mmH₂O | 0.1471118271 mmHg |
| 5 mmH₂O | 0.3677795676 mmHg |
| 10 mmH₂O | 0.7355591353 mmHg |
| 15 mmH₂O | 1.103338703 mmHg |
| 20 mmH₂O | 1.471118271 mmHg |
| 25 mmH₂O | 1.838897838 mmHg |
| 30 mmH₂O | 2.206677406 mmHg |
| 50 mmH₂O | 3.677795676 mmHg |
| 75 mmH₂O | 5.516693515 mmHg |
| 100 mmH₂O | 7.355591353 mmHg |
| 150 mmH₂O | 11.03338703 mmHg |
| 200 mmH₂O | 14.71118271 mmHg |
| 250 mmH₂O | 18.38897838 mmHg |
| 300 mmH₂O | 22.06677406 mmHg |
| 500 mmH₂O | 36.77795676 mmHg |
| 1000 mmH₂O | 73.55591353 mmHg |
| 2000 mmH₂O | 147.1118271 mmHg |
| 5000 mmH₂O | 367.7795676 mmHg |
| 10000 mmH₂O | 735.5591353 mmHg |
Where it's used
Millimeters of Water are used for fan static pressure and duct design in Asia and Europe, while millimeters of mercury appear in blood pressure (e.g. 120/80 mmHg). Both measure pressure, stress and differential pressure (force per unit area), so the conversion is a fixed factor.
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 millimeters of mercury are in 1 millimeter of water?
1 mmH₂O = 0.07355591353 mmHg.
How do I convert millimeters of water to millimeters of mercury?
Multiply the value in mmH₂O by 0.07355591353, or divide it by 13.5951. For example, 15 mmH₂O × 0.07355591353 = 1.103338703 mmHg.
Is the mmH₂O to mmHg 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, "millimeter of mercury, conventional (mmHg)".
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 Millimeters of Mercury. Retrieved October 17, 2026, from https://scientificconverters.com/pressure/millimeter-of-water-to-millimeter-of-mercury/
IEEE
Scientific Converters, "Convert Millimeters of Water to Millimeters of Mercury," scientificconverters.com. Accessed: Oct. 17, 2026. [Online]. Available: https://scientificconverters.com/pressure/millimeter-of-water-to-millimeter-of-mercury/