Atmosphere (atm): A unit of pressure defined as being precisely equal to the mean atmospheric pressure at sea level on Earth; it equals to approximately 101.325 kPa.
Pascal (Pa): The SI unit of pressure, equivalent to one newton per square meter (N/m²).
Millimeter of Mercury (mmHg): A unit of pressure where one mmHg is defined as the amount of force exerted by a column of mercury one millimeter high; it closely approximates one torr.