Universal Pressure Converter

Pressure is force spread over area, and the ten columns on this page exist because a dozen trades each settled on a different scale for it: psi in hydraulics and tyres, bar across European industry, mmHg at the bedside, torr in vacuum work, inches of mercury in aviation and weather, inches of water column in duct balancing, and pascals wherever SI rules. The pascal is the base. Several factors are exact by definition, as NIST's SI conversion guide (Special Publication 811) documents — the standard atmosphere is precisely 101,325 Pa and the bar precisely 100,000 Pa — while others encode a physical reference: inH2O at 249.089 Pa assumes water near 4 °C, and shifting that reference to 60 °F moves it by about a tenth of a percent. Note that mmHg and torr are given the same 133.322 Pa factor, so those two columns will always agree here even though the strict definitions differ by roughly one part in seven million.

The omission that actually bites is gauge versus absolute. Nothing on this page knows which you have. A tyre reading of 32 psi is gauge, meaning 32 above ambient, and its absolute equivalent is nearer 46.7 psia; the converter will faithfully scale whichever number you type without adding or removing an atmosphere for you.