How many psi is 1 inHg?

At 0°C/32°F, 1 inch of mercury is about 0.4911 psi. At 60°F, 1 inHg is about 0.4898 psi.

Why does inHg to psi depend on temperature?

Because the density of mercury is slightly temperature-dependent, the pressure represented by a 1-inch column changes a little. That’s why some tables specify 0°C/32°F and some 60°F.

Can I convert psi to inHg?

Yes, this calculator also supports the reverse conversion from psi to inHg.

inHg to psi Converter (inch of mercury → PSI)

Formulas

1 inHg (32°F) = 3386.389 Pa = 0.491097 psi

1 inHg (60°F) = 3376.85 Pa ≈ 0.48977 psi

psi = inHg × factor_psi

inHg = psi ÷ factor_psi

If your source does not specify temperature, 0°C/32°F is a safe default. Some industrial/aviation charts use 60°F — hence the toggle above.

inHg → psi table (32°F)

inHg	psi	kPa

Values use 0°C/32°F factor. For 60°F, results are ≈0.27% lower.

Where is inHg used?

You’ll see inches of mercury on barometers, vacuum gauges, some HVAC/AC service manuals, and occasionally in aviation altimetry/pressure discussions (though inHg there is often used as a pressure reading, not a column of mercury).

Why convert to psi?

psi is the “common language” for mechanics, automotive boost/vacuum, pneumatics and many US industrial systems. Converting brings the reading into the same unit as your other instruments.

Tips

Check your reference temperature.
State gauge vs absolute if you’re reporting to others.
For vacuum work, note that 29.92 inHg ≈ 14.7 psi ≈ 1 atm.

FAQ

1. Is 29.92 inHg really 14.7 psi?

Yes — at standard atmosphere (0°C), 29.92 inHg corresponds to 1 atm ≈ 14.6959 psi. That’s why the factor is ~0.4911.

2. Why do calculators give slightly different results?

They may be using 32°F vs 60°F, or using rounded values for atmospheric pressure. Our tool shows both.