Convert Inches of Water to Inches of Mercury
Convert Inches of Water (inH₂O) to Inches of Mercury (inHg) instantly and accurately.
Conversion Formula
inHg = inH₂O × 0.07355591353
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 Inches of Mercury
One inch of mercury (inHg) ≈ 3,386 Pa - the primary barometric pressure unit in US aviation and meteorology. ASOS weather stations, METARs, and altimeter settings in the US report in inHg. Standard sea-level pressure is 29.92 inHg. Altimeters are set to local QNH in inHg to maintain altitude reference. US barometers for home weather stations display inHg. Typical pressure range: 28.5-31.0 inHg in continental weather systems. Record low: ~25.70 inHg (Typhoon Tip, 1979). 1 inHg = 3,386.39 Pa.
Quick Reference Table
| Inches of Water (inH₂O) | Inches of Mercury (inHg) |
|---|---|
| 1 inH₂O | 0.0735559 inHg |
| 2 inH₂O | 0.147112 inHg |
| 5 inH₂O | 0.36778 inHg |
| 10 inH₂O | 0.735559 inHg |
| 25 inH₂O | 1.8389 inHg |
| 50 inH₂O | 3.6778 inHg |
| 100 inH₂O | 7.35559 inHg |