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Absolute Pressure Formula:
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Absolute pressure is the total pressure measured relative to a perfect vacuum (zero pressure). It is the sum of gauge pressure (measured relative to atmospheric pressure) and atmospheric pressure. At sea level, standard atmospheric pressure is approximately 14.7 pounds per square inch (psi).
The calculator uses the absolute pressure formula:
Where:
Explanation: This conversion accounts for the atmospheric pressure that surrounds us, which gauge pressure measurements do not include.
Details: Accurate pressure conversion is essential in various engineering applications, including HVAC systems, pneumatic controls, hydraulic systems, and scientific experiments where precise pressure measurements are critical.
Tips: Enter gauge pressure in psig (pounds per square inch gauge). The calculator will automatically add standard atmospheric pressure (14.7 psi) to provide the absolute pressure in psia.
Q1: Why is atmospheric pressure 14.7 psi?
A: This is the average atmospheric pressure at sea level. Actual atmospheric pressure varies with altitude and weather conditions.
Q2: How does altitude affect this conversion?
A: At higher altitudes, atmospheric pressure decreases. For precise calculations at different elevations, use the local atmospheric pressure instead of 14.7 psi.
Q3: What's the difference between psig and psia?
A: PSIG (gauge pressure) is measured relative to atmospheric pressure, while PSIA (absolute pressure) is measured relative to a perfect vacuum.
Q4: When should I use absolute pressure vs gauge pressure?
A: Use absolute pressure for scientific calculations involving gas laws, while gauge pressure is typically used for most industrial and mechanical applications.
Q5: Can this calculator be used for negative gauge pressures?
A: Yes, the calculator works for vacuum measurements (negative gauge pressure) which will result in absolute pressures less than 14.7 psia.