Inches of Water to PSI Converter

The Inches of Water to PSI Converter converts pressure from inches of water column (inH&sub2;O or iwc) to pounds per square inch (PSI). The conversion factor is 1 inH&sub2;O = 0.0360912 PSI. This is a critical conversion for HVAC, gas piping, and cleanroom engineering professionals in the United States.

Inches of water column is the standard pressure unit for low-pressure gas systems in the US. Natural gas delivery to residential and commercial buildings is typically at 5–7 inH&sub2;O (0.18–0.25 PSI). This low pressure unit provides the precision needed to measure and regulate the small pressure differentials that govern gas flow to furnaces, water heaters, and stoves.

In HVAC engineering, duct static pressure, filter pressure drop, and room pressurization are measured in inches of water column. A typical supply duct operates at 0.5–2.0 inH&sub2;O (0.018–0.072 PSI). Cleanrooms require precise pressure differentials — ISO Class 5 rooms maintain 0.02–0.05 inH&sub2;O positive pressure relative to adjacent spaces. These small pressures are much easier to express in inH&sub2;O than in PSI.

Industrial applications also rely on inH&sub2;O for measuring pressure drops across filters, orifice plates, and venturi flow meters. Building fire safety codes specify stairwell pressurization requirements in inH&sub2;O. Our converter provides output in both PSI and Pascals, bridging the gap between US and international engineering specifications.