500 mm Hg (millimeters of mercury) is a unit of pressure. Here's what it equals in other units:

* 66.66 kPa (kilopascals): This is the most common unit of pressure used in the metric system.

* 4.91 psi (pounds per square inch): This is the standard unit of pressure in the US customary system.

* 0.658 atm (atmospheres): This is a unit of pressure often used in chemistry.

Important Note: 500 mm Hg is a relatively high pressure. For reference, standard atmospheric pressure at sea level is 760 mm Hg.