Convert Millimeters of Water to Millibars
Convert Millimeters of Water (mmH₂O) to Millibars (mbar) instantly and accurately.
Conversion Formula
mbar = mmH₂O × 0.0980665
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 Millibars
A millibar (mbar) = 100 Pa = 1 hPa - the historically dominant meteorological pressure unit. Standard sea-level pressure is 1013.25 mbar. Hurricane intensity is characterised by central pressure: Category 5 storms typically below 920 mbar (US record: 892 mbar, 1935). Upper-air analysis levels - 850, 700, 500, 300, 200 mbar - appear throughout decades of archived meteorological data. Aircraft cabins are pressurised to ~750-800 mbar at cruise altitude. 'Weather bombs' see pressure fall 24+ mbar in 24 hours. 1 mbar = 100 Pa.
Quick Reference Table
| Millimeters of Water (mmH₂O) | Millibars (mbar) |
|---|---|
| 1 mmH₂O | 0.0980665 mbar |
| 2 mmH₂O | 0.196133 mbar |
| 5 mmH₂O | 0.490333 mbar |
| 10 mmH₂O | 0.980665 mbar |
| 25 mmH₂O | 2.45166 mbar |
| 50 mmH₂O | 4.90332 mbar |
| 100 mmH₂O | 9.80665 mbar |