To convert bar to psi, multiply by 14.503774. 1 bar equals 14.503774 psi, about the same as the atmosphere at sea level.
| bar | psi |
|---|---|
| 1 bar | 14.503774 psi |
| 2 bar | 29.007548 psi |
| 5 bar | 72.518869 psi |
| 10 bar | 145.03774 psi |
| 25 bar | 362.59434 psi |
| 50 bar | 725.18869 psi |
| 100 bar | 1,450.3774 psi |
| 250 bar | 3,625.9434 psi |
| 500 bar | 7,251.8869 psi |
| 1000 bar | 14,503.774 psi |
Definition: A bar is defined as exactly 100,000 pascals - close enough to Earth's average sea-level atmospheric pressure (1 atm is about 1.01325 bar) that "1 bar" feels roughly like normal outdoor pressure.
History: Norwegian meteorologist Vilhelm Bjerknes - one of the founders of modern weather forecasting - introduced the bar in 1909, named from the Greek "baros" (weight), specifically because meteorologists needed a pressure unit that lined up neatly with everyday atmospheric conditions.
Current use: European tire pressure gauges, espresso machines (a good shot typically pulls at around 9 bar), scuba depth gauges, and industrial pressure equipment.
Definition: The pressure created by one pound of force pushing on one square inch of area.
History: PSI grew out of the imperial engineering tradition - especially the steam engine era, when engineers needed a practical way to describe boiler pressure using units they already had (pounds and inches) rather than inventing something new.
Current use: Car and bike tire pressure gauges in the US, home plumbing and HVAC systems, and scuba tank ratings are all commonly quoted in PSI.
The factor is 14.5038, which is derived rather than defined, so any decimal you see has been rounded somewhere.
No simple round multiplier is close enough to be useful, so this is one to look up rather than estimate. The exact factor is 14.5038.
The reverse factor is 0.069, so one psi is that many bar. Two decimal places is plenty for most purposes, and three is more than a tape measure can justify.
To anchor the scale: 1 bar is about 14.5 psi.