what is atm pressure

Atmospheric pressure, often referred to as air pressure or barometric pressure, is the force per unit area exerted by the weight of the air column above a location on Earth. The standard unit for this is the atmosphere (atm). One standard atmosphere is defined as 101,325 Pascals (Pa), which is approximately the average pressure at mean sea level. This pressure is mainly caused by the gravitational pull on atmospheric gases and decreases as altitude increases.