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

Formula

inH₂O (60 °F) = mmHg × 0.5357755482037

or inH₂O (60 °F) = mmHg ÷ 1.866453225334

Derivation from SI units:

• 1 mmHg = 13 595.1 kg/m³ × 9.80665 m/s² × 0.001 m = 133.322387415 Pa
• 1 inH₂O (60 °F) ≈ 999.0 kg/m³ × 9.80665 m/s² × 0.0254 m ≈ 248.84 Pa
• 1 mmHg = 133.322387415 Pa ÷ 248.84 Pa per inH₂O (60 °F) = 0.5357755482037 inH₂O (60 °F)

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

Worked examples

1. A reading of 80 mmHg converts to 42.86204386 inH₂O (60 °F).
   80 mmHg × 0.5357755482 = 42.86204386 inH₂O (60 °F)
2. A value of 160 mmHg is 85.72408771 inH₂O (60 °F).
   160 mmHg × 0.5357755482 = 85.72408771 inH₂O (60 °F)

Where it's used

Millimeters of Mercury are used for blood pressure (e.g. 120/80 mmHg), 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.

Millimeter 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, "millimeter of mercury, conventional (mmHg)".
• 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.