Gauge Pressure VS Absolute Pressure

Gauge Pressure VS Absolute Pressure

Pressure can be defined as the force used on the area. There are several pressure gauging determinations, but the gauge and absolute pressures are the most typical among the others.

It is significant to define what pressure reference you need to choose, as these gaugings have different and crucial aspects during their usage. If you are mistaken, it may cause several errors during gauging. That is why it is significant to differentiate them properly.

Understanding Gauge Pressure Principle

The most enforced pressure reference is gauge pressure marked with “g” after the pressure unit (for instance 40 psig). Gauge pressure is defined according to the ambient air pressure. The output of the gauge pressure-sensing element is dependent on the air pressure due to the weather conditions. If the gauge pressure is high then the ambient pressure is specified as a positive one. The gauge pressure that is lower than air pressure is known as vacuum gauge pressure. 

Gauge pressure sensing elements typically have a one-pressure port. The ambient air pressure is targeted through a vent hole or tube to the sensing element’s back. A vented gauge pressure transmitter provides the external air pressure to be revealed to the negative position of the pressure sensing diaphragm in the way it defines it concerning the ambient barometric pressure.

A sealed gauge reference differs from the air pressure being sealed on the negative diaphragm position. Gauging hydraulic pressures are specified as high-pressure usages when the air pressure changes cause slight effects on the precision of the sensing. The sealed-gauge pressure is the type of pressure defined through a sealed device in which the zero point is set.

Absolute Pressure Gauge

Pressure is often measured by calculating the distortion of the sensing element where one side of the sensing element contacts with the media process and the other side of the element is revealed to the referred pressure. Gauge pressure is defined according to the ambient pressure reference. Absolute pressure refers to the exposed inner side of the sensing element. If gauge pressure is zeroed against ambient air pressure, it will be referred to as zero against a vacuum. As a result, absolute pressure will be similar to the gauge pressure with air pressure.

It is required to apply a sensing element that defines the gauge pressure if the needed or controlled pressure is not dependent on changes in air pressure. When you need to define the pressure depending on air pressure- you will need to define the air pressure itself.

Absolute Pressure Gauge

Absolute pressure gauges are generally enforced in laboratories where air pressure is required to be defined precisely and is marked as PSIA.


The tire pressure gauge is relative to the gauge pressure and marked as PSIG. The tire is constructed by the principle of avoiding air pressure and assigned zero to the value. 

At this point, you're probably eager to dispense with abbreviations and get to some meaningful pressure calculations. Nevertheless, PSIA (absolute pressure) is the sum of the atmospheric and gauge pressures.

Formula: PSIA = PSIG + air pressure

So, the tire is inflated to the gauge pressure of 32 psi or marked as PSIG of 32. The air pressure is 14.7. The absolute pressure is 32 + 14/7 = 46.7 absolute pressure of psi or PSIA of 46,7.


We hope that you’ve found out all the difference between two major pressure measures: gauge and absolute. Several basic terms are enforced to understand the principle of every aspect of certain pressures and how to use these aspects in practice.

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