Convert Inches of Water to Technical Atmospheres
Convert Inches of Water (inH₂O) to Technical Atmospheres (at) instantly and accurately.
Conversion Formula
at = inH₂O × 0.00254
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 Technical Atmospheres
One technical atmosphere (at) = exactly 1 kgf/cm² = 98,066.5 Pa ≈ 0.968 standard atmospheres. The metric technical pressure unit used in pre-SI European and Japanese engineering for boilers, hydraulic cylinders, and compressed gas systems. A steam boiler at 10 at operates at 0.981 MPa; hydraulic presses are rated at 200-600 at. Still used parenthetically in old German and Japanese machinery manuals and standards (DIN 1301-3 legacy). Converts simply from kgf/cm²: 1 at ≡ 1 kgf/cm². 1 at = 98,066.5 Pa.
Quick Reference Table
| Inches of Water (inH₂O) | Technical Atmospheres (at) |
|---|---|
| 1 inH₂O | 0.00254 at |
| 2 inH₂O | 0.00508 at |
| 5 inH₂O | 0.0127 at |
| 10 inH₂O | 0.0254 at |
| 25 inH₂O | 0.0635 at |
| 50 inH₂O | 0.127 at |
| 100 inH₂O | 0.254 at |