PSI to bar and kPa tyre pressure converter

psi to bar

One psi (pound-force per square inch) is 6.894757 kPa, the factor the international unit tables give. A bar is exactly 100 kPa, so one psi is 0.0689 bar and one bar is 14.5 psi. To go from psi to bar, divide by 14.5: 32 psi is 2.21 bar. To go back, multiply: 2.4 bar is 34.8 psi. For kPa, multiply the bar figure by 100, so 2.21 bar is 221 kPa.

The arithmetic is easy to get slightly wrong at a petrol pump, and the error matters more than it looks. Half a bar is more than 7 psi, the gap between a correctly inflated tyre and one that is wearing its shoulders and costing fuel. If your gauge and your placard use different units, convert the placard figure once, write it down, and set every tyre to that.

Reading a placard in kPa

Many carmakers print the placard in kPa first with psi alongside, as in 230 kPa (33 psi), while the air machine at the fuel station works in psi. If the placard gives only kPa, divide by 6.895: 230 kPa is 33.4 psi, so set 33. Digital gauges usually switch between psi, bar and kPa with a button, which is worth checking before you trust a reading that looks oddly low or high.

All these figures are gauge pressure: the pressure above the air around you, which is what every tyre gauge and air machine reads. Check them cold, before the car has done more than a couple of kilometres, because a warm tyre reads several psi higher.