Pressure
Convert millimetre of mercury (mmHg) to inch of mercury (inHg). Pressure is force per unit area. Process engineers move constantly between SI (kPa, bar) and US (psi) units, and between absolute and gauge.
1 mmHg = 0.03937007 inHg
To convert millimetre of mercury to inch of mercury, multiply the mmHg value by 0.03937007. To go the other way, divide by 0.03937007 (or multiply by 25.4).
| mmHg | inHg |
|---|---|
| 1 | 0.03937007 |
| 2 | 0.07874015 |
| 5 | 0.1968504 |
| 10 | 0.3937007 |
| 25 | 0.9842519 |
| 50 | 1.968504 |
| 100 | 3.937007 |
| 250 | 9.842519 |
| 500 | 19.68504 |
| 1000 | 39.37007 |
Line and vessel ratings, pump discharge heads, and relief set points are all specified in pressure units — usually psi or barg in the field and kPa in calculations.
Always track whether a value is absolute or gauge: 0 barg equals about 101.3 kPa absolute, and mixing the two is a common and costly error.
Worked example. A pressure of 7500.616 mmHg is 295.2998 inHg.
Multiply the value in mmHg by 0.03937007 to get inHg. For example, 10 mmHg = 0.3937007 inHg.
1 mmHg equals 0.03937007 inHg.
Line and vessel ratings, pump discharge heads, and relief set points are all specified in pressure units — usually psi or barg in the field and kPa in calculations.