Convert Inches of Mercury to Inches of Water (60 °F)

Formula

inH₂O (60 °F) = inHg × 13.60869892437

Derivation from SI units:

• 1 inHg = 13 595.1 kg/m³ × 9.80665 m/s² × 0.0254 m = 3386.388640341 Pa
• 1 inH₂O (60 °F) ≈ 999.0 kg/m³ × 9.80665 m/s² × 0.0254 m ≈ 248.84 Pa
• 1 inHg = 3386.388640341 Pa ÷ 248.84 Pa per inH₂O (60 °F) = 13.60869892437 inH₂O (60 °F)

One unit is a measured value, so the factor is approximate. Inch of Mercury definition: inch of mercury; Inch of Water (60 °F) definition: inch of water (60 °F).

Worked examples

1. A reading of 15 inHg converts to 204.1304839 inH₂O (60 °F).
   15 inHg × 13.60869892 = 204.1304839 inH₂O (60 °F)
2. A value of 29 inHg is 394.6522688 inH₂O (60 °F).
   29 inHg × 13.60869892 = 394.6522688 inH₂O (60 °F)

Where it's used

Inches of Mercury are used for aircraft altimeter settings (standard 29.92 inHg), while inches of water (60 °F) appear in older US gas-industry and flow-meter references. 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, "inch of water (60 °F)".

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