Convert Millimeters of Water to Torr
Convert Millimeters of Water (mmH₂O) to Torr (Torr) instantly and accurately.
Conversion Formula
Torr = mmH₂O × 0.07355592401
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 Torr
The torr is defined as exactly 1/760 of a standard atmosphere ≈ 133.322 Pa - effectively replacing mmHg with an exact definition. Named after Evangelista Torricelli (1608-1647), inventor of the barometer. Vacuum science universally uses torr: rough vacuum 760-1 torr; medium vacuum 1-10⁻³ torr; high vacuum 10⁻³-10⁻⁷ torr; ultra-high vacuum below 10⁻⁹ torr. UHV systems for surface science, particle accelerator beam tubes, and space simulation chambers reach 10⁻¹¹-10⁻¹² torr. 1 torr = 133.322 Pa.
Quick Reference Table
| Millimeters of Water (mmH₂O) | Torr (Torr) |
|---|---|
| 1 mmH₂O | 0.0735559 Torr |
| 2 mmH₂O | 0.147112 Torr |
| 5 mmH₂O | 0.36778 Torr |
| 10 mmH₂O | 0.735559 Torr |
| 25 mmH₂O | 1.8389 Torr |
| 50 mmH₂O | 3.6778 Torr |
| 100 mmH₂O | 7.35559 Torr |