What does mmHg stand for?

The term mmHg stands for millimeters of mercury. This unit of measurement is used primarily to quantify pressure, often in the context of measuring blood pressure or the pressure of gases. It originated from the use of mercury in barometers and other pressure-measuring devices because mercury is a dense liquid that allows for precise measurements of atmospheric pressure as it displaces the liquid column in response to changes in pressure.

When measuring blood pressure, for instance, a sphygmomanometer indicates the pressure applied by blood against the walls of arteries in mmHg, reflecting how high the mercury rises in the device's column under that pressure. This makes it an essential unit in both medical and scientific contexts for understanding gas pressure and fluid dynamics.