Common units atmospheres absolute pressure , gauge pressure defined , the pressure Surrounded by a thick layer of the Earth's surface atmospheric pressure on the Earth's surface or the surface of the object caused called " pressure ." Symbol pb; Acts directly on the surface of the pressure vessel or object , called "absolute pressure" , the absolute value of an absolute vacuum pressure as a starting point , the symbol for pa; Measured out with pressure gauge, vacuum gauge , U -shaped pipe pressure instrument called " gauge pressure ", " gauge pressure " as a starting point to atmospheric pressure , the sign bit pg. The relationship between the three is Pa = pb + pg Pressure is the force per unit area of a pressure unit N/m2, denoted by pa, called Pascal. Widely used in engineering MPa ( MPa ) 1MPa = 106Pa 1 atm = 0.1013MPa 1kPa = 1000Pa = 0.01kgf/cm2 1MPa = 106Pa = 10.2kgf/cm2 In the old system of units , the pressure is usually kgf/cm2 ( kgf / cm ) for the unit . People often daily work habits to describe the amount of pressure in kilograms , they are translated into : 1 kg = 1Bar = 0.1Mpa