Convert Torr to Millimeters of Water

Formula

mmH₂O = Torr × 13.59509806316

Derivation from SI units:

• 1 Torr = 101325/760 Pa = 133.3223684 Pa (1/760 of a standard atmosphere)
• 1 mmH₂O = 1000 kg/m³ × 9.80665 m/s² × 0.001 m = 9.80665 Pa
• 1 Torr = 133.3223684211 Pa ÷ 9.80665 Pa per mmH₂O = 13.59509806316 mmH₂O

Both units are defined exactly, so the factor is exact. Torr definition: torr; Millimeter of Water definition: millimeter of water.

Worked examples

1. A reading of 0.1 Torr converts to 1.359509806 mmH₂O.
   0.1 Torr × 13.59509806 = 1.359509806 mmH₂O
2. A value of 100 Torr is 1359.509806 mmH₂O.
   100 Torr × 13.59509806 = 1359.509806 mmH₂O

Where it's used

Torr are used for vacuum technology and vacuum gauges, while millimeters of water appear in fan static pressure and duct design in Asia and Europe. Both measure pressure, stress and differential pressure (force per unit area), so the conversion is a fixed factor.

Torr to other pressure units

Frequently asked questions

Sources

• Guide for the Use of the International System of Units (SI), NIST Special Publication 811, 2008 Edition, National Institute of Standards and Technology , Appendix B.8, "torr (Torr)".
• Guide for the Use of the International System of Units (SI), NIST Special Publication 811, 2008 Edition, National Institute of Standards and Technology , Appendix B.8, "millimeter of water, conventional (mmH2O)".

Last reviewed: 2026-10-15. Factors are stored exactly and computed with 50-digit decimal arithmetic. See how we verify conversion factors.