Convert Centimeters of Mercury to Millimeters of Water
Convert Centimeters of Mercury (cmHg) to Millimeters of Water (mmH₂O) instantly and accurately.
Conversion Formula
mmH₂O = cmHg × 135.951
About Centimeters of Mercury
One centimetre of mercury (cmHg) = 10 mmHg ≈ 1,333.22 Pa. Historical medical and physiological literature used cmHg for intracardiac and intravascular pressures before mmHg became universal. Left ventricular systolic pressure ~12 cmHg; pulmonary artery systolic 2-3 cmHg. Some older European cardiological textbooks and pre-1970s surgical literature report pressures in cmHg. Central venous pressure, cerebral perfusion pressure, and intra-abdominal pressure are occasionally cited in cmHg in legacy datasets. 1 cmHg = 1,333.22 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
| Centimeters of Mercury (cmHg) | Millimeters of Water (mmH₂O) |
|---|---|
| 1 cmHg | 135.951 mmH₂O |
| 2 cmHg | 271.902 mmH₂O |
| 5 cmHg | 679.755 mmH₂O |
| 10 cmHg | 1359.51 mmH₂O |
| 25 cmHg | 3398.78 mmH₂O |
| 50 cmHg | 6797.55 mmH₂O |
| 100 cmHg | 13595.1 mmH₂O |