Convert Torr to Millimeters of Water
Convert Torr (Torr) to Millimeters of Water (mmH₂O) instantly and accurately.
Conversion Formula
mmH₂O = Torr × 13.59509806
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.
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
| Torr (Torr) | Millimeters of Water (mmH₂O) |
|---|---|
| 1 Torr | 13.5951 mmH₂O |
| 2 Torr | 27.1902 mmH₂O |
| 5 Torr | 67.9755 mmH₂O |
| 10 Torr | 135.951 mmH₂O |
| 25 Torr | 339.877 mmH₂O |
| 50 Torr | 679.755 mmH₂O |
| 100 Torr | 1359.51 mmH₂O |