1. What is PSIG and PSIA?

PSIG Definition: Pounds per square inch gauge (PSIG) is the pressure measured relative to atmospheric pressure.

PSIA Definition: Pounds per square inch absolute (PSIA) is the pressure measured relative to a perfect vacuum.

Purpose: This calculator converts between gauge pressure (PSIG) and absolute pressure (PSIA).

2. How Does the Conversion Work?

The conversion uses the formula:

Where:

• 14.7 psi — Standard atmospheric pressure at sea level
• PSIG — Gauge pressure (relative to atmospheric pressure)
• PSIA — Absolute pressure (relative to perfect vacuum)

Explanation: Absolute pressure equals gauge pressure plus atmospheric pressure.

3. Importance of Pressure Conversion

Details: Proper pressure conversion is essential for engineering calculations, HVAC systems, pneumatic systems, and scientific applications where absolute pressure is required.

4. Using the Calculator

Tips: Simply enter the PSIG value and the calculator will automatically compute the PSIA value. The calculation works for both positive and negative PSIG values.

5. Frequently Asked Questions (FAQ)

Q1: Why is 14.7 psi used as atmospheric pressure?
A: This is the standard atmospheric pressure at sea level. Actual atmospheric pressure varies with altitude and weather conditions.

Q2: What's the difference between PSIG and PSIA?
A: PSIG measures pressure relative to atmospheric pressure, while PSIA measures pressure relative to absolute vacuum.

Q3: Can PSIG be negative?
A: Yes, negative PSIG represents vacuum conditions (pressure below atmospheric).

Q4: When would I need to use PSIA instead of PSIG?
A: PSIA is used in scientific calculations, gas laws, and any application where absolute pressure is required (e.g., compressor calculations).

Q5: Does altitude affect this conversion?
A: Yes, at higher altitudes atmospheric pressure decreases, so the conversion factor would be less than 14.7 psi.