Key idea: Atmospheric pressure is caused by the weight of the atmosphere pushing down on itself and on the surface below it. Pressure is defined as the force acting on an object divided by the area upon which the force is acting.
What is the value of atmospheric pressure?
Standard atmosphere. The standard atmosphere (symbol: atm) is a unit of pressure defined as 101325 Pa (1.01325 bar), equivalent to 760 mmHg (torr), 29.92 inches Hg and 14.696 psi.