Convert Millimeters of Mercury to Inches of Water
Convert Millimeters of Mercury (mmHg) to Inches of Water (inH₂O) instantly and accurately.
Conversion Formula
inH₂O = mmHg × 0.5352401575
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 Inches of Water
One inch of water column (inH₂O or in WC) = pressure from 1 inch of fresh water at standard gravity ≈ 249.09 Pa. The standard unit for low-pressure measurement in US HVAC and plumbing: ductwork static pressure, fan performance, filter ratings, and gas appliance manifold pressures are all specified in inches WC. Household natural gas supply pressure is typically 7 in WC (0.25 psi). Blower door tests for building air-tightness use 50 Pa ≈ 0.2 in WC test pressure. 1 inH₂O = 249.089 Pa.
Quick Reference Table
| Millimeters of Mercury (mmHg) | Inches of Water (inH₂O) |
|---|---|
| 1 mmHg | 0.53524 inH₂O |
| 2 mmHg | 1.07048 inH₂O |
| 5 mmHg | 2.6762 inH₂O |
| 10 mmHg | 5.3524 inH₂O |
| 25 mmHg | 13.381 inH₂O |
| 50 mmHg | 26.762 inH₂O |
| 100 mmHg | 53.524 inH₂O |