Convert Inches of Water to Millimeters of Mercury
Convert Inches of Water (inH₂O) to Millimeters of Mercury (mmHg) instantly and accurately.
Conversion Formula
mmHg = inH₂O × 1.868320204
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.
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.
Quick Reference Table
| Inches of Water (inH₂O) | Millimeters of Mercury (mmHg) |
|---|---|
| 1 inH₂O | 1.86832 mmHg |
| 2 inH₂O | 3.73664 mmHg |
| 5 inH₂O | 9.3416 mmHg |
| 10 inH₂O | 18.6832 mmHg |
| 25 inH₂O | 46.708 mmHg |
| 50 inH₂O | 93.416 mmHg |
| 100 inH₂O | 186.832 mmHg |