-- most common unit of pressure is the atmosphere

-- an atmosphere is the average pressure at sea level

-- atmosphere is abbreviated atm

-- the SI unit of pressure is pascal

-- pascal is abbreviated pa

-- 1 Pa = 1 N/m^2

-- 1 atm = 101,325 Pa

-- millimeter of mercury comes from how pressure is measured with a barometer

-- millimeter of mercury is abbreviated mmHg

-- millimeter of mercury is also called a torr

-- 1 atm = 760 mmHg

-- 1 mmHg = 1 torr

-- inches of mercury is abbreviated in.Hg

-- pounds per square inch is abbreviated psi

-- 1 atm = 29.92 in. Hg

-- 1 atm = 14.7 psi