1. What is PSIG and PSIA?

PSIG (pounds per square inch gauge) measures pressure relative to atmospheric pressure, while PSIA (pounds per square inch absolute) measures pressure relative to a perfect vacuum.

2. How Does the Conversion Work?

The conversion uses the simple formula:

Where:

• 14.7 psi — Standard atmospheric pressure at sea level
• PSIG — Gauge pressure reading
• PSIA — Absolute pressure result

Explanation: Absolute pressure includes atmospheric pressure while gauge pressure excludes it.

3. Importance of Pressure Conversion

Details: Many engineering calculations require absolute pressure values, particularly in thermodynamics, fluid dynamics, and gas law calculations.

4. Using the Calculator

Tips: Simply enter the gauge pressure in PSIG and the calculator will provide the equivalent absolute pressure in PSIA.

5. Frequently Asked Questions (FAQ)

Q1: Why is 14.7 psi used as atmospheric pressure?
A: This is the average atmospheric pressure at sea level, though actual local pressure may vary slightly.

Q2: Does altitude affect this conversion?
A: Yes, at higher altitudes atmospheric pressure decreases, so the constant would be smaller than 14.7.

Q3: What's the difference between PSI and PSIG?
A: In many contexts, PSI is used interchangeably with PSIG, though technically PSI could refer to either absolute or gauge pressure.

Q4: When would I need PSIA instead of PSIG?
A: PSIA is needed for calculations involving gas laws (like Boyle's Law), thermodynamics, and any system where absolute pressure matters.

Q5: Can this calculator work in reverse (PSIA to PSIG)?
A: Yes, simply subtract 14.7 from the PSIA value to get PSIG.