Convert Torr to Inches of Water

Formula

inH₂O = Torr × 0.5352400812266

or inH₂O = Torr ÷ 1.868320469775

Derivation from SI units:

• 1 Torr = 101325/760 Pa = 133.3223684 Pa (1/760 of a standard atmosphere)
• 1 inH₂O = 1000 kg/m³ × 9.80665 m/s² × 0.0254 m = 249.08891 Pa
• 1 Torr = 133.3223684211 Pa ÷ 249.08891 Pa per inH₂O = 0.5352400812266 inH₂O

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

Worked examples

1. A reading of 0.1 Torr converts to 0.05352400812 inH₂O.
   0.1 Torr × 0.5352400812 = 0.05352400812 inH₂O
2. A value of 100 Torr is 53.52400812 inH₂O.
   100 Torr × 0.5352400812 = 53.52400812 inH₂O

Where it's used

Torr are used for vacuum technology and vacuum gauges, while inches of water appear in HVAC total external static pressure (residential ≈ 0.5 inH₂O). 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, "inch of water, conventional (inH2O)".

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