Convert Torr to Inches of Mercury

Formula

inHg = Torr × 0.03937007313125

or inHg = Torr ÷ 25.40000361864

Derivation from SI units:

• 1 Torr = 101325/760 Pa = 133.3223684 Pa (1/760 of a standard atmosphere)
• 1 inHg = 13 595.1 kg/m³ × 9.80665 m/s² × 0.0254 m = 3386.388640341 Pa
• 1 Torr = 133.3223684211 Pa ÷ 3386.388640341 Pa per inHg = 0.03937007313125 inHg

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

Worked examples

1. A reading of 0.1 Torr converts to 0.003937007313 inHg.
   0.1 Torr × 0.03937007313 = 0.003937007313 inHg
2. A value of 100 Torr is 3.937007313 inHg.
   100 Torr × 0.03937007313 = 3.937007313 inHg

Where it's used

Torr are used for vacuum technology and vacuum gauges, while inches of mercury appear in aircraft altimeter settings (standard 29.92 inHg). 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 mercury, conventional (inHg)".

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