Pound per Square Inch (psi)

Definition

Pound per square inch (psi) is a unit of pressure defined as one pound-force applied to an area of one square inch. It is part of the Imperial system, commonly used in the United States but not recognized as an SI unit.

History

The concept of pressure measurement dates back to the 17th century, with the invention of the barometer. The psi measurement became popular in the 19th century, especially in engineering and industrial applications, as steam engines and pneumatic systems evolved.

Uses

Psi is widely used in various fields, including automotive (tire pressure), engineering (material stress testing), and HVAC systems. It is prevalent in the U.S. and some other countries that use Imperial measurements.

Conversions

  • 1 psi = 6894.76 pascals (Pa)
  • 1 psi = 0.070307 megapascals (MPa)
  • 1 psi = 0.0689476 atm (atmospheres)

Fun Facts

  • A common misconception is that psi is always the same as atmospheric pressure, but it varies based on altitude and weather.
  • The term "pound-force" can be confusing; it refers to the force exerted by gravity on a one-pound mass.
Calculator – MinyTools