A pound-force per square inch gauge, or psig conversion, is the conversion of pressure represented in other units to pressure represented in psig, or vice versa. Psig is a unit of pressure relative to the surrounding atmosphere.
Bar, atmosphere, torr and pounds per square inch are common units of pressure. One psig equals 0.0689476 bars, 0.068046 atmospheres, 51.7149 torrs and 0.0193368 pounds per square inch. This data can be used to convert psig to any of these units and vice versa.
Psig is sometimes represented as "lb/in²." It has a scale factor of 6894.757, which means 1 psig equals 6894.757 pascals. In contrast, pounds per square inch absolute, or psia, measures pressure relative to a vacuum rather than in ambient atmospheric pressure. At sea level, earth's atmosphere exerts a pressure of 14.7 psi. Humans do not feel this pressure because the internal pressure of liquids in their bodies counteracts the external pressure.
A pressure gauge calibrated to read 0 in vacuum would read 14.7 psi at sea level. This means that a reading of 30 psig on a tire gauge represents an absolute pressure of 44.7 psi.
The SI unit for pressure is the pascal. One pascal is equal to 0.000145037738007 psig.