In which unit is atmospheric pressure usually measured?

Atmospheric pressure is commonly measured in multiple units, but one of the most traditional and widely recognized units is in terms of Mercury (Hg). This measurement stems from the use of mercury barometers, where the height of a column of mercury provides a direct measurement of atmospheric pressure.

The standard atmospheric pressure at sea level is defined as 760 mm of Hg, which corresponds to the height of the mercury column that can be supported by the atmospheric pressure. This method has historical significance and practicality, which is why it remains a familiar reference in meteorology and aviation.

Understanding that atmospheric pressure can also be expressed in Pascals and millibars—a millibar being equivalent to 100 Pascals—provides a broader context. However, Mercury remains a fundamental reference point due to its long-standing use and the physical principles it illustrates, such as the behavior of fluids under pressure. Barometric pressure encapsulates the concept of atmospheric pressure but is more of a descriptive term than a specific measurement unit.

Therefore, the choice of Mercury (Hg) is well-founded in the context of traditional measurements of atmospheric pressure.