Pressure is force divided by the area it acts on, which is why a narrow heel exerts far more pressure on the floor than a flat shoe. Your car's door placard says psi, the pump at a European garage shows bar, a lot of modern gauges show kPa - same pressure, three different numbers.
| psi | bar | kPa |
|---|---|---|
| 30 | 2.07 | 206.8 |
| 32 | 2.21 | 220.6 |
| 35 | 2.41 | 241.3 |
| 38 | 2.62 | 262.0 |
Most passenger cars run 30-35 psi (about 2.1-2.4 bar / 207-241 kPa); SUVs and light trucks often run higher, 35-44 psi. Always use the pressure on your vehicle's door placard or owner's manual, not the maximum figure printed on the tire sidewall - that's the tire's limit, not the recommended setting. Check pressure cold, before driving or after the car has sat for a few hours; driving heats tires and can raise the reading by 4-6 psi, which would give a falsely high number.
A different, related question - how much pressure a weight puts on the surface below it, given the contact area. Useful for load-spreading questions (a crane mat, a tracked vehicle) rather than tire inflation.
A 20-tonne excavator on two wide tracks (3.355m x 0.6m each) puts down about 48.7 kPa of ground pressure - similar to a person walking. The same weight on a small footprint would be dramatically higher: a person standing in narrow stiletto heels can put over 13 MPa on the ground at the point of contact, hundreds of times more than the same person's weight spread across a flat shoe. This is exactly why tracked vehicles use wide tracks instead of narrow wheels on soft ground, and why a crane needs a mat under its outriggers.
Divide by 14.5038. Thirty-five psi is about 2.41 bar. Car door placards usually quote psi, while European pumps often show bar.
Use the figure on the placard inside your driver’s door or in the owner’s manual - not the maximum printed on the tyre sidewall, which is a limit rather than a recommendation. Most passenger cars sit around 30-35 psi.
Each of these has its own page with the exact factor, a reference table and the working shown. The converter above handles any of them too - these exist so the specific answer is one click rather than a search.