The millimeter of mercury (mmHg) is a pressure unit equal to about 133.322 pascals, traditionally used in medicine for measuring blood pressure and in meteorology for barometric readings. A normal adult blood pressure of 120/80 mmHg is universally understood by healthcare professionals, making this unit a fixture in clinical settings. One mmHg equals approximately 0.01934 psi or 0.1333 kPa.

The torr is a pressure unit named after Evangelista Torricelli, equal to approximately 133.322 pascals, used primarily in vacuum physics and high-altitude research. It is nearly identical to the millimeter of mercury, with one torr defined as exactly 1/760 of a standard atmosphere. Vacuum pumps, electron microscopes, and semiconductor manufacturing equipment commonly specify operating pressures in torr.