Science, Tech, Math › Social Sciences What Is PSI? Share Flipboard Email Print Ian Lishman / Getty Images Social Sciences Environment Alternative Fuels Climate Change Green Living Health Pollution Preservation & Conservation Psychology Sociology Archaeology Economics Ergonomics Maritime by Christine & Scott Gable Christine and Scott Gable are automobile hybrid and alternative fuel experts who have brewed biodiesel in their basement and traveled125,000 miles on waste vegetable oil. Updated October 21, 2017 The acronym PSI stands for "Pounds per Square Inch," and is the common unit of measurement for pressure. It can be understood as the amount of force that is exerted on an area of one square inch. Normal atmospheric pressure at sea level is 14.7 PSI. Pronunciation: Pronounce each letter individually: P - S - I. Example: Normal tire pressure is usually about 32 PSI. Continue Reading