Convert Millimeters of Mercury to Millimeters of Water
Convert Millimeters of Mercury (mmHg) to Millimeters of Water (mmH₂O) instantly and accurately.
Conversion Formula
mmH₂O = mmHg × 13.5951
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 Millimeters of Water
One millimetre of water column (mmH₂O) = pressure from 1 mm of fresh water at standard gravity = exactly 9.80665 Pa. Preferred for very low differential pressures in HVAC: ductwork static pressures, fan curves, filter resistance, and building pressurisation are in mm WC. Gas valve operating pressures are typically 0.5-3 mm WC; clean-room cascade differentials 12-25 mm WC. A domestic gas hob manifold operates at ~20 mm WC on natural gas. Also used in spirometer calibration and hospital oxygen delivery systems. 1 mmH₂O = 9.80665 Pa.
Quick Reference Table
| Millimeters of Mercury (mmHg) | Millimeters of Water (mmH₂O) |
|---|---|
| 1 mmHg | 13.5951 mmH₂O |
| 2 mmHg | 27.1902 mmH₂O |
| 5 mmHg | 67.9755 mmH₂O |
| 10 mmHg | 135.951 mmH₂O |
| 25 mmHg | 339.878 mmH₂O |
| 50 mmHg | 679.755 mmH₂O |
| 100 mmHg | 1359.51 mmH₂O |