Convert psi to bars

The formula

bars = psi × 0.068947573

psi to bars — quick reference

A psi recommendation on a car whose placard is in bar

An American owner’s manual, a tyre shop’s chart or a forum post quotes psi, while the digital gauge sold across Europe and the pressure display built into many European cars read bar. 35 psi is 2.41 bar, and the working range for ordinary cars occupies a narrow band between roughly 2.0 and 2.6 bar.

That narrowness is the whole point of converting carefully. A full bar of error is enormous, the difference between a correct tyre and a badly wrong one, whereas the same span expressed in psi is fifteen units and looks like a rounding decision. In bar the decimal place carries real weight: 2.4 against 2.2 is an adjustment, not noise.

The number moulded into the tyre wall is not the number to use

Tyre sidewalls carry a maximum pressure, often 44 or 51 psi, which is a limit for the tyre in isolation rather than a recommendation for the car it is fitted to. The figure to follow is the vehicle manufacturer’s, on the door pillar, inside the fuel filler flap or in the manual, because it is matched to that car’s weight and suspension.

Gauges also report pressure above atmospheric rather than absolute, which is why a flat tyre reads zero instead of about 14.7 psi. Check cold: a tyre warmed by half an hour of driving reads several psi high, and letting air out to hit the target leaves it soft afterwards. Many placards print kPa alongside, where 100 kPa is exactly 1 bar.

Questions