Convert Millimeters of Mercury to Feet of Water
Convert Millimeters of Mercury (mmHg) to Feet of Water (ftH₂O) instantly and accurately.
Conversion Formula
ftH₂O = mmHg × 0.04460334646
About Millimeters of Mercury
One millimetre of mercury (mmHg) = pressure from 1 mm of mercury at 0°C and standard gravity = 133.322 Pa. Clinical medicine worldwide uses mmHg for blood pressure (normal ~120/80 mmHg) and for gas partial pressures in physiology: arterial O₂ ~95-100 mmHg; CO₂ ~40 mmHg; alveolar O₂ ~104 mmHg. Ophthalmologists measure intraocular pressure in mmHg (normal 10-21; glaucoma risk above 21). Vacuum equipment ratings are also given in mmHg. 760 mmHg = 1 atm. 1 mmHg = 133.322 Pa.
About Feet of Water
One foot of water column (ftH₂O) ≈ 2,989 Pa - the US customary equivalent of cmH₂O used in civil and hydraulic engineering. Municipal water supply systems are designed for 40-80 psi head ≈ 92-184 ft; fire suppression sprinkler systems require minimum 7 psi ≈ 16 ft. Well pump specifications, sump pump head ratings, irrigation mainline pressure, and drainage calculations all use feet of head. 1 ft of water = 12 in WC = 0.4335 psi ≈ 2,989 Pa.
Quick Reference Table
| Millimeters of Mercury (mmHg) | Feet of Water (ftH₂O) |
|---|---|
| 1 mmHg | 0.0446033 ftH₂O |
| 2 mmHg | 0.0892067 ftH₂O |
| 5 mmHg | 0.223017 ftH₂O |
| 10 mmHg | 0.446033 ftH₂O |
| 25 mmHg | 1.11508 ftH₂O |
| 50 mmHg | 2.23017 ftH₂O |
| 100 mmHg | 4.46033 ftH₂O |