Convert Inches of Water to Pounds per Square Inch
Convert Inches of Water (inH₂O) to Pounds per Square Inch (psi) instantly and accurately.
Conversion Formula
psi = inH₂O × 0.036127292
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 Pounds per Square Inch
One pound per square inch (psi) ≈ 6,894.76 Pa - the dominant pressure unit in US industry and consumer products. Car tyres: 32-36 psi; truck tyres 80-120 psi; bicycle road tyres 80-130 psi. Home water supply: 40-80 psi; residential maximum 80 psi per plumbing code. Compressed air tools: 90-150 psi. Steam autoclave sterilisation: 15-30 psi. The distinction between gauge (psig) and absolute (psia) pressure is critical: gauge pressure is relative to ambient; absolute = gauge + ~14.696 psi. 1 psi = 6,894.76 Pa.
Quick Reference Table
| Inches of Water (inH₂O) | Pounds per Square Inch (psi) |
|---|---|
| 1 inH₂O | 0.0361273 psi |
| 2 inH₂O | 0.0722546 psi |
| 5 inH₂O | 0.180636 psi |
| 10 inH₂O | 0.361273 psi |
| 25 inH₂O | 0.903182 psi |
| 50 inH₂O | 1.80636 psi |
| 100 inH₂O | 3.61273 psi |