# PSI vs. PSIG: What's the Difference?

Edited by Huma Saeed || By Sawaira Riaz || Published on February 11, 2024
PSI (Pounds per Square Inch) is a unit of pressure relative to the surrounding atmosphere, while PSIG (Pounds per Square Inch Gauge) measures pressure relative to atmospheric pressure.

## Key Differences

PSI, or Pounds per Square Inch, is a unit that measures pressure by calculating the force in pounds exerted on one square inch of area. PSIG, or Pounds per Square Inch Gauge, is a similar measurement but it specifically denotes pressure measurements that are above atmospheric pressure, effectively discounting atmospheric pressure from its reading.
Sawaira Riaz
Feb 11, 2024
PSI is used to express absolute pressure, which includes the pressure exerted by the atmosphere. In contrast, PSIG is the pressure reading given by most pressure gauges, as it subtracts atmospheric pressure and focuses on the pressure exerted by the system itself.
Huma Saeed
Feb 11, 2024
For example, a tire pressure gauge reading in PSIG does not include atmospheric pressure; if it reads zero, it means the pressure inside the tire is the same as the atmospheric pressure. However, if a tire's pressure were measured in PSI (absolute pressure), the reading would be higher, including the atmospheric pressure.
Sawaira Riaz
Feb 11, 2024
Understanding the difference between PSI and PSIG is crucial in fields like engineering, where precise pressure measurements are essential. For instance, in a closed system where external atmospheric conditions do not affect the pressure, PSI may be more relevant, whereas PSIG is more applicable in open systems interacting with atmospheric pressure.
Sawaira Riaz
Feb 11, 2024
Atmospheric pressure at sea level is approximately 14.7 PSI. So, a reading of 30 PSIG is actually equivalent to 44.7 PSI (30 + 14.7). This distinction is important in applications such as compressed air systems, hydraulic systems, and refrigeration.
Janet White
Feb 11, 2024

## Comparison Chart

### Definition

Measures absolute pressure, including atmospheric
Measures pressure above atmospheric pressure
Sawaira Riaz
Feb 11, 2024

### Atmospheric Pressure

Included in the measurement
Not included, measured against atmospheric
Sawaira Riaz
Feb 11, 2024

### Typical Use

In scenarios requiring absolute pressure readings
Common in everyday pressure gauges
Sawaira Riaz
Feb 11, 2024

Higher than PSIG for the same condition
Lower than PSI due to atmospheric pressure exclusion
Aimie Carlson
Feb 11, 2024

### Application

Scientific research, closed systems
General use, open systems interacting with atmosphere
Janet White
Feb 11, 2024

## PSI and PSIG Definitions

#### PSI

PSI is crucial for accurate readings in closed systems.
The vessel was pressurized to 100 PSI for the experiment.
Sawaira Riaz
Jan 15, 2024

#### PSIG

PSIG measures pressure relative to atmospheric pressure.
The car tire was inflated to 32 PSIG.
Sawaira Riaz
Jan 15, 2024

#### PSI

PSI includes the atmospheric pressure in its reading.
At sea level, atmospheric pressure is about 14.7 PSI.
Aimie Carlson
Jan 15, 2024

#### PSIG

PSIG is used in systems where atmospheric pressure affects readings.
The pool's filtration system operates at 20 PSIG.
Harlon Moss
Jan 15, 2024

#### PSI

PSI is a standard unit for measuring pressure in various fields.
The hydraulic system operates at a maximum of 2500 PSI.
Sawaira Riaz
Jan 15, 2024

#### PSIG

PSIG readings are lower than PSI for the same condition due to atmospheric pressure exclusion.
The gauge showed a drop in pressure to 15 PSIG.
Sawaira Riaz
Jan 15, 2024

#### PSI

PSI measures the absolute pressure exerted on a square inch of area.
The laboratory equipment was calibrated to 150 PSI.
Huma Saeed
Jan 15, 2024

#### PSIG

PSIG is commonly used in everyday applications like tire pressure.
The air compressor shut off automatically at 120 PSIG.
Sawaira Riaz
Jan 15, 2024

#### PSI

PSI is used in scientific and engineering contexts for precise pressure measurement.
The boiler's safety valve is set to release at 200 PSI.
Aimie Carlson
Jan 15, 2024

#### PSIG

PSIG is important for measurements in open systems.
The boiler's operating pressure was maintained at 50 PSIG.
Sawaira Riaz
Jan 15, 2024

#### PSI

The 23rd letter of the Greek alphabet. See Table at alphabet.
Sawaira Riaz
Jan 15, 2024

#### PSI

Parapsychological phenomena or abilities considered as a group.
Sawaira Riaz
Jan 15, 2024

#### PSI

(countable) The twenty-third letter of Classical and Modern Greek and the twenty-fifth letter of Old and Ancient Greek.
Sawaira Riaz
Jan 15, 2024

#### PSI

A form of psychic energy.
Sawaira Riaz
Jan 15, 2024

#### PSI

A unit of pressure
Sawaira Riaz
Jan 15, 2024

#### PSI

The 23rd letter of the Greek alphabet
Sawaira Riaz
Jan 15, 2024

## FAQs

#### How does PSI differ from PSIG?

PSI includes atmospheric pressure in its measurement, while PSIG does not.
Sawaira Riaz
Feb 11, 2024

#### Is PSI or PSIG more common in car tire pressure?

Car tire pressure is typically measured in PSIG.
Janet White
Feb 11, 2024

#### What does PSI stand for?

Pounds per Square Inch.
Sawaira Riaz
Feb 11, 2024

#### What is the main use of PSIG?

PSIG is mainly used in pressure gauges for everyday applications.
Huma Saeed
Feb 11, 2024

#### Do pressure cookers use PSI or PSIG?

Pressure cookers commonly use PSI for pressure measurement.
Aimie Carlson
Feb 11, 2024

#### In what scenario would PSIG read zero?

PSIG would read zero when the pressure inside a system equals atmospheric pressure.
Janet White
Feb 11, 2024

#### How do I convert PSIG to PSI?

Add the atmospheric pressure (approximately 14.7 at sea level) to the PSIG value.
Janet White
Feb 11, 2024

#### Is atmospheric pressure always considered in PSI?

Yes, PSI measurements always include atmospheric pressure.
Aimie Carlson
Feb 11, 2024

#### What is the atmospheric pressure in PSI at sea level?

Approximately 14.7 PSI.
Janet White
Feb 11, 2024

#### Can PSI and PSIG have the same numerical value?

Yes, but only if the atmospheric pressure is zero, which is practically impossible.
Aimie Carlson
Feb 11, 2024

#### Can PSIG readings be negative?

No, PSIG readings represent pressure above atmospheric and cannot be negative.
Sawaira Riaz
Feb 11, 2024

#### Why is PSI used in hydraulic systems?

PSI is used for its accuracy in measuring absolute pressure in closed systems.
Sawaira Riaz
Feb 11, 2024

#### Is PSIG dependent on altitude?

Yes, as atmospheric pressure changes with altitude, affecting PSIG readings.
Aimie Carlson
Feb 11, 2024

#### How does temperature affect PSI and PSIG?

Temperature changes can affect the volume and pressure of gases, impacting both PSI and PSIG readings.
Harlon Moss
Feb 11, 2024

#### Is PSI used in the aviation industry?

Yes, for measuring cabin pressure and other critical systems.
Sawaira Riaz
Feb 11, 2024

#### How is PSIG useful in automotive applications?

It's used for measuring tire pressure, oil pressure, and fuel pressure, among others.
Sawaira Riaz
Feb 11, 2024

#### Is PSI important in scientific research?

Yes, PSI is crucial for precise pressure measurements in scientific research.
Harlon Moss
Feb 11, 2024

#### Why is PSI used in scientific equipment calibration?

For its precision and ability to provide absolute pressure readings.
Sawaira Riaz
Feb 11, 2024

#### Is PSIG used in weather forecasting?

No, meteorologists typically use other units like millibars or inches of mercury.
Sawaira Riaz
Feb 11, 2024

#### Are PSI and PSIG interchangeable?

They are not interchangeable as they measure different types of pressure.
Janet White
Feb 11, 2024