Convert Inches of Mercury to Inches of Water
Convert Inches of Mercury (inHg) to Inches of Water (inH₂O) instantly and accurately.
Conversion Formula
inH₂O = inHg × 13.5951
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.
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
| Inches of Mercury (inHg) | Inches of Water (inH₂O) |
|---|---|
| 1 inHg | 13.5951 inH₂O |
| 2 inHg | 27.1902 inH₂O |
| 5 inHg | 67.9755 inH₂O |
| 10 inHg | 135.951 inH₂O |
| 25 inHg | 339.877 inH₂O |
| 50 inHg | 679.755 inH₂O |
| 100 inHg | 1359.51 inH₂O |