PSIG to PSIA Converter

Pounds per Square Inch Gauge (PSIG) measures pressure relative to the surrounding ambient air pressure, meaning a gauge reading of zero indicates atmospheric conditions. Pounds per Square Inch Absolute (PSIA), on the other hand, measures pressure relative to a complete vacuum. To convert from PSIG to PSIA, you simply add the local atmospheric pressure to your gauge pressure using the standard formula: PSIA = PSIG + Atmospheric Pressure. Standard atmospheric pressure is commonly approximated as 14.696 psi at sea level.

Imagine you are monitoring a compressed air tank at a manufacturing facility operating at sea level. Your mechanical pressure gauge displays a reading of 100 PSIG. To determine the absolute internal pressure of the tank, you apply the formula using standard sea-level atmospheric pressure (14.7 psi). First, take your PSIG value of 100. Next, add the atmospheric pressure of 14.7. The resulting absolute pressure is 114.7 PSIA, giving you the true force exerted on the tank walls from a complete vacuum reference.

Always account for altitude changes when performing precise pressure conversions, as atmospheric pressure drops significantly as elevation increases. Verify whether your instrumentation requires sea-level standard or your exact local barometric pressure for optimal engineering safety. Keep units consistent across all calculations to avoid costly system design errors.