# Pound-force per square inch

Physical unit
Unit name Pound-force per square inch
Unit symbol ${\ displaystyle \ mathrm {psi, lb.p.sq.in., psia, psig}}$ Physical quantity (s) pressure
Formula symbol ${\ displaystyle p}$ dimension ${\ displaystyle {\ mathsf {M \; L ^ {- 1} \; T ^ {- 2}}}}$ system Anglo-American system of measurement
In SI units ${\ displaystyle \ mathrm {1 \, psi \ approx 6 \, 895 \; Pa}}$ Derived from Pound-force , square inch

Pound-force per square inch , or pounds per square inch (" pounds per square inch "), is a unit of measurement commonly used in the United States for pressure . It is a unit of the Anglo-American system of measurement that does not belong to the international system of units (SI) . It is used in the USA for pressure specifications in everyday life. One example is tire pressure . The SI unit Pascal is mostly used in science .

Pound-force per square inch is defined as the pressure exerted by the weight of a mass of one Anglo-American pound (lb) at standard acceleration on an area of ​​one square inch. The designation of the unit is lb.p.sq.in., psi or psi for short . This is short for "pound-force per square inch".

Conversion into other units of the Anglo-American system of measurement:

1 lb.p.sq.in. = 1 psi = 144  lb.p.sq.ft = 1/2000  tn.sh. p.sq.in = 1/2240  tn. p.sq.in

With the standard acceleration of fall and the conversion of kg , the conversion factor from psi to the international system of units results: ${\ displaystyle g_ {n} = 9 {,} 80665 \; \ mathrm {m} / \ mathrm {s} ^ {2}}$ ${\ displaystyle 1 \; \ mathrm {lb} = 0 {,} 4536}$ ${\ displaystyle 1 \, \ mathrm {psi} \; = \; 1 \, {\ frac {\ mathrm {lbf}} {\ mathrm {in} ^ {2}}} \; = \; 1 \, { \ frac {\ mathrm {lb} \ cdot g_ {n}} {\ mathrm {in} ^ {2}}} \; \ approx \; 6 \, 895 \; \ mathrm {Pa} \; \ approx \; 0 {,} 07 \; \ mathrm {bar}}$ In the opposite direction, the conversion factor is:

${\ displaystyle \ mathrm {1 \, Pa} \ approx 1 {,} 4504 \ cdot 10 ^ {- 4} \; \ mathrm {psi}}$ ${\ displaystyle \ mathrm {1 \, bar} \ approx 14 {,} 5 \; \ mathrm {psi}}$ Often the unit is specified even more precisely with psia (pounds-force per square inch absolute) for the absolute pressure or psig (pounds-force per square inch gauge) for the relative pressure (overpressure) To characterize the pressure measurement method, according to the - outdated - German terms ata and atü for atmosphere absolute or overpressure.

For larger pressures or tensions, the unit kilopound per square inch (ksi) (1 ksi = 1000 psi) is used in some cases .