1. What is PSIA vs PSIG?

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

2. How Does the Calculator Work?

The calculator uses the simple conversion formula:

Where:

• 14.7 psi — Standard atmospheric pressure at sea level
• PSIA — Absolute pressure (including atmospheric pressure)
• PSIG — Gauge pressure (excluding atmospheric pressure)

Explanation: To convert between absolute and gauge pressure, you simply add or subtract atmospheric pressure (14.7 psi at sea level).

3. Importance of Pressure Conversion

Details: Understanding the difference between absolute and gauge pressure is crucial in engineering, HVAC systems, industrial processes, and scientific applications where accurate pressure measurements are required.

4. Using the Calculator

Tips: Enter the pressure value in psi, select the conversion direction (PSIG to PSIA or PSIA to PSIG), and click calculate. All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: Why is atmospheric pressure 14.7 psi?
A: This is the standard atmospheric pressure at sea level, representing the weight of Earth's atmosphere above that point.

Q2: Does atmospheric pressure change with altitude?
A: Yes, atmospheric pressure decreases with increasing altitude. The 14.7 psi standard is for sea level.

Q3: When should I use PSIA vs PSIG?
A: Use PSIG for most pressure measurements (tire pressure, system pressure). Use PSIA for scientific calculations where absolute pressure is needed.

Q4: Can PSIG be negative?
A: Yes, negative PSIG represents vacuum pressure (pressure below atmospheric).

Q5: What's the difference between PSI and PSIG?
A: In most practical contexts, PSI and PSIG are used interchangeably to mean gauge pressure.