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 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.