Convert Technical Atmospheres to Millimeters of Water
Convert Technical Atmospheres (at) to Millimeters of Water (mmH₂O) instantly and accurately.
Conversion Formula
mmH₂O = at × 10000
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.
About Millimeters of Water
One millimetre of water column (mmH₂O) = pressure from 1 mm of fresh water at standard gravity = exactly 9.80665 Pa. Preferred for very low differential pressures in HVAC: ductwork static pressures, fan curves, filter resistance, and building pressurisation are in mm WC. Gas valve operating pressures are typically 0.5-3 mm WC; clean-room cascade differentials 12-25 mm WC. A domestic gas hob manifold operates at ~20 mm WC on natural gas. Also used in spirometer calibration and hospital oxygen delivery systems. 1 mmH₂O = 9.80665 Pa.
Quick Reference Table
| Technical Atmospheres (at) | Millimeters of Water (mmH₂O) |
|---|---|
| 1 at | 10000 mmH₂O |
| 2 at | 20000 mmH₂O |
| 5 at | 50000 mmH₂O |
| 10 at | 100000 mmH₂O |
| 25 at | 250000 mmH₂O |
| 50 at | 500000 mmH₂O |
| 100 at | 1000000 mmH₂O |