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PSIG to PSIA

PSIG to PSIA

Use local atmospheric pressure for precise results.

Precision: 3

Gauge pressure relative to ambient air.

Absolute pressure referenced to a perfect vacuum.

Tip: PSIA = PSIG + P_atm.

Formula: PSIA = PSIG + P_atm

How PSIG → PSIA Conversion Works

PSIA (absolute) is referenced to a perfect vacuum; PSIG (gauge) is referenced to the surrounding air. They differ by the local atmospheric pressure:

At sea level, P_atm ≈ 14.6959 psi. At higher altitudes, P_atm is lower, so the same PSIG corresponds to a lower PSIA.

Frequently Asked Questions

Is 14.7 PSIA equal to 0 PSIG?
Yes—under sea-level standard conditions, a system at atmospheric pressure reads ≈14.7 PSIA and 0 PSIG.
Are PSIA and PSIG the same?
No. PSIA is absolute (vacuum reference). PSIG is gauge (ambient reference). Use PSIA for thermodynamics and when altitude matters.
What does 14.7 PSIA mean?
It’s the absolute pressure at sea level in standard conditions—air pressing with 14.7 pounds per square inch above vacuum.
Is 14.7 PSIA atmospheric pressure?
It’s the widely used standard reference for sea level. Real atmospheric pressure varies with weather and altitude.