Convert Pounds per Square Inch to Torr

The Pound per Square Inch (symbol: psi) is a unit of pressure. An imperial unit of pressure equal to one pound-force applied over one square inch (exactly 6,894.757 Pa per NIST SP 811). PSI is the dominant US pressure unit and remains the working unit in most US-built industrial, automotive, and consumer equipment: passenger-car tire inflation (32-35 psi cold), compressed air shop systems (typically 100-150 psi), hydraulic equipment (1,500-3,000 psi mobile, up to 10,000 psi on press brakes), ammunition chamber pressures (SAAMI specs in psi), municipal potable water supply (~40-80 psi at the meter), and natural gas distribution pressures. US engineering textbooks and the ASME B31 pipe codes, API piping specifications, and AWWA waterworks standards quote allowable pressures in psi. Engineers should distinguish gauge psi (psig — pressure above atmospheric) from absolute psi (psia — pressure above perfect vacuum); 0 psig = 14.696 psia at sea level. 1 psi = 6.895 kPa = 0.0689 bar = 51.715 mmHg.

It belongs to the imperial measurement system.

Pounds per Square Inch are commonly used in tire inflation, weather reporting, scuba diving, and engineering.

The Torr (symbol: torr) is a unit of pressure. A unit of pressure defined as exactly 1/760 of a standard atmosphere (≈ 133.322 Pa). Named after 17th-century physicist Evangelista Torricelli, who in 1643 invented the mercury barometer while studying why suction-lift pumps fail above ~10 m — establishing that the atmosphere itself has weight. The torr is the primary unit in modern vacuum technology and semiconductor fabrication: a "rough vacuum" is ~1 torr, "medium vacuum" 10⁻³ torr (typical of mechanical-pump-only systems), "high vacuum" 10⁻⁶ torr (achievable with turbomolecular pumps, used in mass spectrometry and electron microscopy), and "ultrahigh vacuum" (UHV) 10⁻⁹ torr or lower (semiconductor MBE, surface science, particle accelerators). Manufacturing fabs quote chamber pressures in torr or mTorr (10⁻³ torr) at every process step. Numerically the torr is almost identical to the mmHg (1 torr ≈ 1.000000 mmHg under modern definitions; historically they differed by 0.000015%).

Torr are commonly used in tire inflation, weather reporting, scuba diving, and engineering.