The bar is a metric pressure unit equal to 100,000 pascals, widely used in meteorology, oceanography, and industrial applications because it closely approximates atmospheric pressure at sea level. Tire pressure gauges in Europe, scuba diving depth ratings, and weather maps all commonly reference bars or millibars. One bar equals approximately 0.9869 atmospheres or 14.504 psi.

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.