PSI vs. PSIG: Know the Difference
By Shumaila Saeed || Published on February 20, 2024
PSI measures pressure relative to atmospheric pressure, while PSIG denotes pressure gauge readings above atmospheric pressure.
Key Differences
PSI, or Pounds per Square Inch, is a unit of pressure relative to the atmospheric pressure. It's a basic measure used in various fields like automotive, industrial, and meteorological applications. PSIG, or Pounds per Square Inch Gauge, differs as it specifically refers to pressure measured relative to the ambient atmospheric pressure. Essentially, PSIG equals the PSI reading minus the atmospheric pressure.
Shumaila Saeed
Feb 20, 2024
In the context of PSI, the measurement is an absolute value. This means it includes the atmospheric pressure (approximately 14.7 PSI at sea level) in its total. PSIG, however, subtracts this atmospheric pressure from its measurement. It provides a reading of how much pressure is exerted over and above the normal atmospheric pressure.
Shumaila Saeed
Feb 20, 2024
When using PSI, the implication is that the pressure reading includes all pressure in the system, including atmospheric pressure. It's a more encompassing measurement. Conversely, PSIG provides a more specific reading, indicating only the pressure that is above the atmospheric baseline. It's particularly useful in applications where the difference from normal atmospheric pressure is what matters.
Shumaila Saeed
Feb 20, 2024
PSI is commonly used in scientific and engineering calculations where absolute pressure is required. It's essential for calculations where the complete pressure value is necessary. PSIG, on the other hand, is often found in practical applications like air compressors, car tire inflation, and HVAC systems, where relative pressure is more relevant.
Shumaila Saeed
Feb 20, 2024
Understanding the distinction between PSI and PSIG is crucial for accuracy in various fields. Misinterpreting these units can lead to incorrect readings and potential hazards. PSIG is the more common unit in everyday applications, as it gives a clearer indication of the pressure being exerted over the standard atmospheric pressure.
Shumaila Saeed
Feb 20, 2024
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Comparison Chart
Definition
Measures total pressure including atmospheric pressure
Measures pressure over and above atmospheric pressure
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Feb 20, 2024
Usage in Calculations
Used in scientific and engineering contexts for absolute pressure
Common in practical applications for relative pressure
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Feb 20, 2024
Atmospheric Pressure Inclusion
Includes atmospheric pressure in the reading
Excludes atmospheric pressure, measuring only excess pressure
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Feb 20, 2024
Common Applications
Scientific research, deep-sea measurements
Air compressors, tire pressure gauges
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Feb 20, 2024
Importance
Crucial for theoretical and precise calculations
More relevant for everyday, practical applications
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Feb 20, 2024
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PSI and PSIG Definitions
PSIG
Used in systems where atmospheric pressure is a baseline.
The car tires are inflated to 32 PSIG.
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Jan 17, 2024
PSI
Used to quantify internal pressure of a container or system.
The boiler's safety valve is set to release at 150 PSI.
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Jan 17, 2024
PSIG
Indicates pressure differential from the ambient air pressure.
The HVAC system operates at an optimal 20 PSIG.
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Jan 17, 2024
PSI
Measurement of force applied per unit area.
The hydraulic press exerts 2,000 PSI.
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Jan 17, 2024
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PSIG
Pressure measurement above atmospheric pressure.
The air compressor was set to shut off at 100 PSIG.
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Jan 17, 2024
PSI
A standard unit for pressure in the Imperial system.
The gas pipeline operates at 80 PSI.
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Jan 17, 2024
PSIG
A gauge reading of pressure excluding atmospheric pressure.
The pressure gauge reads 50 PSIG in the tank.
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Jan 17, 2024
PSI
Reflects the magnitude of force exerted on a surface.
The diver's watch can withstand pressures up to 300 PSI.
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Jan 17, 2024
PSIG
Commonly used in mechanical and plumbing systems for relative pressure.
The water line pressure was measured at 60 PSIG.
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Jan 17, 2024
PSI
(countable) The twenty-third letter of Classical and Modern Greek and the twenty-fifth letter of Old and Ancient Greek.
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Repeatedly Asked Queries
What is PSI?
PSI stands for Pounds per Square Inch, a unit measuring pressure including atmospheric pressure.
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Feb 20, 2024
How is PSIG different from PSI?
PSIG stands for Pounds per Square Inch Gauge and measures pressure above atmospheric pressure, while PSI includes it.
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Feb 20, 2024
Where is PSI commonly used?
PSI is used in scientific, engineering, and meteorological contexts for absolute pressure measurements.
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Feb 20, 2024
What applications use PSIG?
PSIG is used in practical applications like air compressors and tire pressure gauges.
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Feb 20, 2024
Is PSI or PSIG higher in the same conditions?
PSI is higher as it includes atmospheric pressure, whereas PSIG measures only the pressure above it.
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Feb 20, 2024
Do weather reports use PSI or PSIG?
Weather reports typically use other units like millibars or inches of mercury.
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Feb 20, 2024
Can PSI and PSIG have the same value?
Yes, in a vacuum where atmospheric pressure is zero, PSI and PSIG values can be the same.
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Feb 20, 2024
Why is understanding PSI and PSIG important?
Correct understanding is crucial for safety and accuracy in various applications.
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Feb 20, 2024
How do you convert PSI to PSIG?
Subtract atmospheric pressure (about 14.7 at sea level) from PSI to get PSIG.
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Feb 20, 2024
Is PSIG always less than PSI?
Yes, because PSIG subtracts atmospheric pressure from the total pressure.
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Feb 20, 2024
How is PSIG useful in automotive applications?
PSIG is used to measure tire pressure and engine vacuum.
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Feb 20, 2024
What is a normal atmospheric pressure in PSI?
Normal atmospheric pressure is about 14.7 PSI at sea level.
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Feb 20, 2024
Are there instruments that measure in both PSI and PSIG?
Yes, some pressure gauges can switch between PSI and PSIG readings.
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Feb 20, 2024
Is PSI used in the metric system?
No, PSI is part of the Imperial system; the metric equivalent is Pascals.
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Feb 20, 2024
Is PSIG used in underwater measurements?
No, underwater pressure measurements typically use absolute pressure units like PSI or Pascals.
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Feb 20, 2024
Are PSI and PSIG units interchangeable?
No, they represent different types of pressure measurements.
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Feb 20, 2024
What happens to PSIG at high altitudes?
PSIG readings are not affected by altitude as they are relative to atmospheric pressure.
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Feb 20, 2024
Can atmospheric pressure affect PSIG readings?
No, PSIG readings are independent of atmospheric pressure variations.
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Feb 20, 2024
Does altitude affect PSI measurements?
Yes, PSI measurements can vary with altitude due to changes in atmospheric pressure.
Shumaila Saeed
Feb 20, 2024
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About Author
Written by
Shumaila SaeedShumaila Saeed, an expert content creator with 6 years of experience, specializes in distilling complex topics into easily digestible comparisons, shining a light on the nuances that both inform and educate readers with clarity and accuracy.
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