Atmospheric Pressure And Gauge Pressure

Atmospheric pressure

Atmospheric Pressure
Definition
Atmospheric pressure is the force per unit area exerted against a surface by the weight of air above that surface in the Earth's atmosphere.
Units
Pascal (Pa)
Example
Atmospheric pressure at sea level is approximately 101325 Pa.

Gauge pressure

Gauge Pressure
Definition
Gauge pressure is the pressure relative to the ambient pressure.
Units
Pascal (Pa)
Example
If the atmospheric pressure is 101325 Pa, a tire inflated to a gauge pressure of 200000 Pa is actually at an absolute pressure of 301325 Pa.