Convert Millimeters of Water to Bars
Convert Millimeters of Water (mmH₂O) to Bars (bar) instantly and accurately.
Conversion Formula
bar = mmH₂O × 9.806650000e-5
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.
About Bars
A bar = exactly 100,000 Pa ≈ 0.987 atm - the world standard for industrial pressure outside North America. Hydraulic systems, pneumatic equipment, gas cylinders, dive computers, and tyre gauges in Europe and Asia use bar. Scuba diving: +1 bar per 10 m depth; at 40 m recreational limit = 5 bar absolute. European tyre pressure labels show bar alongside kPa. Industrial processes: steam at 10-50 bar; high-pressure reactors 100-300 bar; water-jet cutting 1,000-4,000 bar. 1 bar = 100,000 Pa = 14.504 psi.
Quick Reference Table
| Millimeters of Water (mmH₂O) | Bars (bar) |
|---|---|
| 1 mmH₂O | 9.807 × 10-5 bar |
| 2 mmH₂O | 0.000196133 bar |
| 5 mmH₂O | 0.000490332 bar |
| 10 mmH₂O | 0.000980665 bar |
| 25 mmH₂O | 0.00245166 bar |
| 50 mmH₂O | 0.00490333 bar |
| 100 mmH₂O | 0.00980665 bar |