Millimetre of mercury
A millimetre of mercury is a manometric unit of pressure, formerly defined as the extra pressure generated by a column of mercury one millimetre high, and currently defined as exactly 133.322387415 pascals[1] or exactly 133.322 pascals.[2] It is denoted mmHg[3] or mm Hg.[4][2]
| millimetre of mercury | |
|---|---|
| Unit of | Pressure |
| Symbol | mmHg or mm Hg |
| Conversions | |
| 1 mmHg in ... | ... is equal to ... |
| SI units | 133.322 Pa |
| English Engineering units | 0.01933678 lbf/in2 |
Although not an SI unit, the millimetre of mercury is still routinely used in medicine, meteorology, aviation, and many other scientific fields.
One millimetre of mercury is approximately 1 Torr, which is 1/760 of standard atmospheric pressure (101325/760 ≈ 133.322368 pascals). Although the two units are not equal, the relative difference (less than 0.000015%) is negligible for most practical uses.