Convert Inches of Mercury to Pascals

Formula

Pa = inHg × 3386.388640341

Derivation from SI units:

• 1 inHg = 13 595.1 kg/m³ × 9.80665 m/s² × 0.0254 m = 3386.388640341 Pa
• 1 Pa = 1 N/m² = 1 kg·m⁻¹·s⁻²

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

Worked examples

1. A reading of 15 inHg converts to 50795.82961 Pa.
   15 inHg × 3386.38864 = 50795.82961 Pa
2. A value of 29 inHg is 98205.27057 Pa.
   29 inHg × 3386.38864 = 98205.27057 Pa

Where it's used

Inches of Mercury are used for aircraft altimeter settings (standard 29.92 inHg), while pascals appear in cleanroom and isolator pressure differentials (typically 10–50 Pa). 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)".
• The International System of Units (SI), 9th edition (SI Brochure), Bureau International des Poids et Mesures , Table 4, coherent derived units with special names.

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