Full name: pound/square inch [gauge]
Plural form: pounds/square inch
Alternate spelling: psig
Category type: pressure
Scale factor: 6894.75728
The SI derived unit for pressure is the pascal.
1 pascal is equal to 0.000145037738007 psig.
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Psig (pound-force per square inch gauge) is a unit of pressure relative to the surrounding atmosphere. By contrast, psia measures pressure relative to a vacuum (such as that in space). At sea level, Earth's atmosphere actually exerts a pressure of 14.7 psi. Humans do not feel this pressure because internal pressure of liquid in their bodies matches the external pressure. If a pressure gauge is calibrated to read zero in space, then at sea level on Earth it would read 14.7 psi. Thus a reading of 30 psig on a tire gauge represents an absolute pressure of 44.7 psi.