Pressure
Convert inch of mercury (inHg) to millimetre of mercury (mmHg). Pressure is force per unit area. Process engineers move constantly between SI (kPa, bar) and US (psi) units, and between absolute and gauge.
1 inHg = 25.4 mmHg
To convert inch of mercury to millimetre of mercury, multiply the inHg value by 25.4. To go the other way, divide by 25.4 (or multiply by 0.03937007).
| inHg | mmHg |
|---|---|
| 1 | 25.4 |
| 2 | 50.80001 |
| 5 | 127 |
| 10 | 254 |
| 25 | 635.0001 |
| 50 | 1270 |
| 100 | 2540 |
| 250 | 6350.001 |
| 500 | 12700 |
| 1000 | 25400 |
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 295.2998 inHg is 7500.616 mmHg.
Multiply the value in inHg by 25.4 to get mmHg. For example, 10 inHg = 254 mmHg.
1 inHg equals 25.4 mmHg.
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.