The pascal (Pa) is the SI base unit of pressure, defined as one newton per square meter, used in physics, engineering, and material science. While it is the scientific standard, everyday pressures are more commonly expressed in kilopascals or megapascals because one pascal represents an extremely small pressure. One pascal equals 0.00001 bar or about 0.000145 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.