Convert Inches of Mercury to Bar

Formula

bar = inHg × 0.03386388640341

or bar = inHg ÷ 29.52998330101

Derivation from SI units:

• 1 inHg = 13 595.1 kg/m³ × 9.80665 m/s² × 0.0254 m = 3386.388640341 Pa
• 1 bar = 10⁵ Pa (exact, by definition)
• 1 inHg = 3386.388640341 Pa ÷ 100000 Pa per bar = 0.03386388640341 bar

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

Worked examples

1. A reading of 15 inHg converts to 0.5079582961 bar.
   15 inHg × 0.0338638864 = 0.5079582961 bar
2. A value of 29 inHg is 0.9820527057 bar.
   29 inHg × 0.0338638864 = 0.9820527057 bar

Where it's used

Inches of Mercury are used for aircraft altimeter settings (standard 29.92 inHg), while bar appear in compressed air and pneumatics (6–8 bar). Both measure pressure, stress and differential pressure (force per unit area), so the conversion is a fixed factor.

Inch of Mercury 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, "inch of mercury, conventional (inHg)".
• 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, "bar".

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