PSIG units are relative to atmospheric pressure. He is also a member of Mensa and the American Parliamentary Debate Association. We use cookies to ensure that we give you the best experience on our website. By continuing to use it, you agree to their use. Regards!!! "A Dictionary of Units of Measurement"; University of North Carolina; 2008, Clarkson University: Conversion Factors for Units; W.R. Wilcox; 2010. For example, you need to make sure that your car tires or bicycle tires are inflated to the proper PSI before you drive or ride, and today, equipment of all types includes pressure sensors or gauges to assist in monitoring and diagnostic operations. You can use the actual atmospheric pressure value for your location if it is available, or you can also use 14.7 psi (the approximate atmospheric pressure at sea level) as a standard value to convert PSIG to PSIA and vice versa. The ambient pressure at sea level is about 14.7 PSIA, but ambient PSIG is always 0. (Unless you live at high altitude or in a deep valley, the sea level value will work.) PSIG is also known as Gauge Pressure. As an example, absolute pressure at sea level is 14.70 PSIA and absolute pressure at an elevation of 1,000 feet is 14.18 PSIA. For example, if you are converting a pressure of 50 psi, then 50 - 14.696 = 35.3. The calculation below shows how kilograms per square centimetre are converted into pounds per square inch by converting each into pascals (SI units for pressure): 1 psi= 6,894.76 pascals (Pa) 1 kg/cm²= 98066.5 pascals (Pa) psi value x 6,894.76 Pa = kg/cm2 value x 98066.5 Pa. psi value = kg/cm2 value x 14.2233. kg/cm² pressure related products. However, now that you know the difference between PSI, PSIA, and PSIG, you can choose the best air pressure measurements for the job you’re doing. It is not required to use psi or bar unless required by the customer. However, PSIG specifies what the measurement is relative to, whereas PSI does not. He has a Bachelor of Science in journalism from Boston University and has written for the American Civil Liberties Union, the marketing firm InSegment and the project management service Assembla. Pounds per square inch absolute (psia) is used to make it clear that the pressure is relative to a vacuum rather than the ambient atmospheric pressure. The formulas to describe the relationship are: PSIG + 1 atm = PSIA and PSIA – 1 atm = PSIG (where atm is atmospheric pressure). The ambient pressure at sea level is about 14.7 PSIA, but ambient PSIG is always 0. That calls for more than a basic formula. They are ways to assess the amount of force that’s exerted in an area. Absolute pressure, which is what "psi" usually represents, takes into account the atmospheric pressure that acts on most objects. PSIA—this designation applies to PSI Absolute. In Imperial units, stress can be measured in pound-force per square inch, which is abbreviated as psi. I joined WIKA in 1999 as an Applications Engineer specializing in Electronic Pressure Measurement. The WIKA news subscription informs you, free of charge, by e-mail whenever there is a new blog article. It refers to pressure in a perfect vacuum. It is easy to calculate PSIA or PSIG or convert between the two. Definition: A pound-force per square inch (symbol: psi) is an imperial and US customary unit of pressure based on avoirdupois units. As altitude goes up, atmospheric pressure goes down. In other words, since atmospheric pressure at sea level is 14.7 PSIA, you subtract the PSIA of 14.7 from an atm pressure of 14.7 to equal zero PSIG (14.7 (PSIA) – 14.7 (atm) = 0). What is pounds per square inch (psi)? Therefore, since the suggested pressure for drive tires is 75 PSIG (80 PSIG for trailer tires), you should check tire pressure and adjust it when they’re cold.