# Pound-force per square inch

Physical unit | |
---|---|

Unit name | Pound-force per square inch |

Unit symbol | |

Physical quantity (s) | pressure |

Formula symbol | |

dimension | |

system | Anglo-American system of measurement |

In SI units | |

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:

In the opposite direction, the conversion factor is:

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gauge) for the relative pressure (overpressure) To characterize the pressure measurement method, according to the - outdated - German terms ata and atü for atmosphere absolute or overpressure.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 .