what is mm hg

Millimeters of mercury (mm Hg) is a unit of pressure that is used to measure the pressure inside a fluid, such as the fluid inside your blood vessels. It is a manometric unit of pressure, formerly defined as the extra pressure generated by a column of mercury one millimeter high, and currently defined as exactly 133.322387415 pascals or exactly 133.322 pascals. The term mm Hg is also used to measure blood pressure, where it represents the pressure exerted by a column of mercury 1 millimeter high at 0°C and under the acceleration of gravity. In medicine and physiology, mm Hg is used to measure blood pressure, and it is often abbreviated as "mmHg" or "mm Hg".