Contact usNews Get Quotes

> News > Industry

What Do PSI, PSIA, and PSIG Mean? A Beginner’s Guide

TIME: 2025.06.24 AUTHOR: Admin NUMBER OF VIEWS 1424
PSI is a common pressure measurement unit in the United States. It is very important to understand its meaning and application in pressure measurement. In this article, we will introduce the concepts of PSI, PSIA and PSIG, their uses and differences.

What is PSI?

PSI is a unit of pressure measurement, which is the abbreviation of Pounds Per Square Inch. It is a relatively common unit of pressure measurement, mainly used in the United States, Canada and the United Kingdom. Generally speaking, people usually use PSI to refer to PSIG, which is the pressure relative to a standard atmospheric pressure. In specific industries, PSIG and PSIA are still distinguished. PSI is mainly used in tire pressure monitoring, hydraulic and pneumatic fields, and industrial manufacturing fields.

PSIA Vs PSIG

PSIA measures the pressure relative to an absolute vacuum, that is, the relative pressure. The PSIA = PSIG + current 1atm (in PSI). A completely sealed container with a vacuum inside has a pressure of 0 PSIA. At sea level, a standard atmospheric pressure is about 14.7 PSIA. It is mainly used in aerospace, HVAC, meteorology and scientific research, vacuum technology and other fields.

PSIG

PSIG refers to the pressure value relative to a standard atmospheric pressure, that is, gauge pressure. Gauge pressure is divided into positive pressure and negative pressure, so PSIG has positive and negative values. The conversion formula is PSIG = PSIA - current 1atm (in PSI). For example, at sea level, the pressure value of a tire is 32 PSIG, and the standard atmospheric pressure at that time is 14.7PSIA, then the actual absolute pressure value is 32+14.7=46.7PSIA.

PSIA PSIG Conversion

As mentioned above, the conversion formula between PSIA and PSIG is:
PSIA = PSIG + current 1atm (in PSI）
 PSIG = PSIA - current 1atm (in PSI)
It can be seen that the value of PSIG is always lower than that of PSIA, so the values between the two are easily interchangeable, provided that you know the local atmospheric pressure value, or you can use a standard atmospheric pressure value (14.7) for estimation.
PSIA = PSIG + 14.7 (in PSI）
PSIG = PSIA - 14.7 (in PSI)

Conclusion

PSI is a universal pressure measurement unit, PSIA and PSIG are two different unit variants. In specific applications, the choice of PSIG or PSIA needs to be determined based on the actual working conditions. Although they are not very different, they are very helpful for us to choose products.

HOT keyword: Pressure Sensor Pressure Transmitter wireless pressure sensor Sputtered Thin Film Pressure Transmitter

PREVThe Ultimate Guide to Pressure Sensor

What's the Difference Between Gauge Pressure and Absolute Pressure? NEXT

Recommend View More
TIME 2026.06.02

China Level Sensor Buying Guide for Beginners

This guide provides procurement managers and engineers with a structured approach to sourcing liquid level measurement equipment from China. It covers operating principles of well level transducers (submersible pressure, ultrasonic, capacitive, radar), key selection criteria, supplier credibility assessment, and total cost of ownership. With a special focus on balancing performance, international certifications (CE, RoHS, ATEX), and real-world installation best practices, the article helps readers achieve cost-effective automation while maintaining process reliability. A spotlight on GAMICOS GLT530 illustrates modern OEM-ready transducer solutions.

TIME 2026.05.19

Why Canada Distributors Source Diesel Level Sensors from China

Canadian distributors source diesel level sensors from China for cost savings, advanced tech, and full certifications.

TIME 2026.05.14

Comparing Quality: US vs Chinese-made Ultrasonic Level Sensors

This article compares US and Chinese ultrasonic level sensors. US models offer superior materials and reliability for high-end applications. Chinese sensors, led by brands like GAMICOS, provide competitive quality, advanced features (IoT, auto-correction), and better cost-effectiveness. The choice depends on specific application needs and budget.

Technical SupportView More
FAQView More
Video CenterView More
Products
Pressure Sensor Pressure Transmitter Level Transmitter Fuel Level Sensor Ultrasonic Level Sensor Radar Level Sensor Water Level Meter Accessories
Solution
Industrial Applications Chemical Vehicles Oil and Gas Food and Medicine Fuel Monitoring Water treatment Machinery Manufaturing Municipal fire Hydrologic monitoring Refrigeration Drilling Exploration
Product Page GLT500 GLT5001 GLTV7 GPT200 GUT741 GLTV7S GLT622 GLT742 GLTV3 GLT744
Support
Technical Solution FAQ Download Video
Service
OEM/ODM Service Our services

GAMICOS-MEAS GAMICOS-ALI GAMICOS-CN GAIMC GALOCE
029-81292510

info@gamicos.com

Rm. 1208, Building B, Huixin IBC, No. 1 Zhang Bayi Road, High-tech Zone, Xi'an, Shaanxi, China

Copyright © Xi'an Gavin Electronic Technology Co., Ltd Site Map

Message Form