Convert Inches of Mercury to Decibars

Formula

dbar = inHg × 0.3386388640341

or dbar = inHg ÷ 2.952998330101

Derivation from SI units:

• 1 inHg = 13 595.1 kg/m³ × 9.80665 m/s² × 0.0254 m = 3386.388640341 Pa
• 1 dbar = 10⁻¹ bar = 10⁴ Pa
• 1 inHg = 3386.388640341 Pa ÷ 10000 Pa per dbar = 0.3386388640341 dbar

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

Worked examples

1. A reading of 15 inHg converts to 5.079582961 dbar.
   15 inHg × 0.338638864 = 5.079582961 dbar
2. A value of 29 inHg is 9.820527057 dbar.
   29 inHg × 0.338638864 = 9.820527057 dbar

Where it's used

Inches of Mercury are used for aircraft altimeter settings (standard 29.92 inHg), while decibars appear in oceanography: CTD instruments report sea pressure in dbar. 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", with SI prefix deci (10⁻¹).

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