Complex sentence: Since atmospheric pressure at sea level is around 14.7 psi, this will be added to any pressure reading made in air at sea levelre inch gauge or pounds per square inch gage (psig), indicating that the pressure is relative to atmospheric pressure.
Split into simpler sentences: Since atmospheric pressure at sea level is around 14.7 psi, this will be added to any pressure reading made in air at sea level. The converse is pounds per square inch gauge or pounds per square inch gage (psig), indicating that the pressure is relative to atmospheric pressure.