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| Inch of mercury | |
|---|---|
_-_DSC06342.JPG) Early American barometer calibrated in inches of mercury | |
| General information | |
| Unit of | Pressure |
| Symbol | inHg, ″Hg |
| Conversions | |
| 1 inHg in ... | ... is equal to ... |
| SI units | 3.38639 kPa |
| United States customary units | 0.491154 psi |
Inch of mercury (inHg and ″Hg) is a non-SI unit of measurement for pressure. It is used for barometric pressure in weather reports, refrigeration and aviation in the United States.
It is the pressure exerted by a column of mercury 1 inch (25.4 mm) in height at the standard acceleration of gravity. Conversion to metric units depends on the density of mercury, and hence its temperature; typical conversion factors are:[1]
| Conditions | Pressure |
|---|---|
| conventional | 3386.389 pascals |
| 32 °F (0 °C) | 3386.38 pascals |
| 60 °F (16 °C) | 3376.85 pascals |
In older literature, an "inch of mercury" is based on the height of a column of mercury at 60 °F (15.6 °C).[1]
- 1 inHg60 °F = 3,376.85 pascals (33.7685 hPa)
In Imperial units: 1 inHg60 °F = 0.489 771 psi, or 2.041 771 inHg60 °F = 1 psi.