Inches of Mercury to PSI Converter
Type a value in either field; the other updates instantly.
1 inHg = 0.491154 psi 1 psi = 2.03602 inHg
Formula
Worked example: 25 inHg × 0.491154 = 12.279 psi
inHg to psi conversion table
| inHg | psi | kPa |
|---|---|---|
| 1 | 0.49115 | 3.3864 |
| 2 | 0.98231 | 6.7728 |
| 5 | 2.4558 | 16.932 |
| 10 | 4.9115 | 33.864 |
| 12 | 5.8939 | 40.637 |
| 15 | 7.3673 | 50.796 |
| 18 | 8.8408 | 60.955 |
| 20 | 9.8231 | 67.728 |
| 22 | 10.805 | 74.501 |
| 24 | 11.788 | 81.273 |
| 25 | 12.279 | 84.66 |
| 26 | 12.77 | 88.046 |
| 27 | 13.261 | 91.433 |
| 28 | 13.752 | 94.819 |
| 29 | 14.243 | 98.205 |
| 29.5 | 14.489 | 99.898 |
| 29.92 | 14.695 | 101.32 |
| 30 | 14.735 | 101.59 |
Where this conversion is used
Inches of mercury (inHg) is common on US vacuum gauges, HVAC manifolds and barometers; psi is used for compressors and process equipment. Because inHg vacuum and psi vacuum are both counted down from atmospheric pressure, the same factor converts gauge readings: 25 inHg vacuum is 12.28 psi below atmosphere.
For absolute pressure (psia), start from absolute inHg: standard sea-level pressure is 29.92 inHg = 14.696 psia. To mix gauge and absolute readings or correct for altitude, use the full vacuum unit converter.
Frequently asked questions
How many psi are in 1 inch of mercury?
1 inHg = 0.491154 psi. In the other direction, 1 psi = 2.03602 inHg.
How do I convert inches of mercury to psi?
Multiply the value in inHg by 0.491154. Example: 25 inHg = 12.279 psi.
How many psi is 29.92 inHg?
29.92 inHg is 14.70 psi, which is standard atmospheric pressure at sea level (14.696 psia).
How do I convert inHg vacuum to psi?
Multiply by 0.4912 to get psi below atmosphere (−psig). For example, 20 inHg vacuum = 9.82 psi vacuum. To get absolute pressure, subtract that from your local atmospheric pressure (14.696 psia at sea level).