Tire Pressure in bar, psi and kPa, Explained
Rent a car abroad or buy a gauge online and you quickly meet three different units for the same thing: bar in most of Europe, psi in the United States, and kPa on many Canadian and Australian tire placards. They all measure the same pressure, so converting between them is simple once you know the factors.
The three units in one minute
- bar: 1 bar = 100,000 pascals, very close to atmospheric pressure at sea level.
- kPa (kilopascal): 1 kPa = 1,000 pascals, so 1 bar = 100 kPa exactly.
- psi (pounds per square inch): 1 psi ≈ 6.895 kPa, so 1 bar ≈ 14.5 psi.
Quick conversions
| bar | kPa | psi |
|---|---|---|
| 2.0 | 200 | 29.0 |
| 2.2 | 220 | 31.9 |
| 2.4 | 240 | 34.8 |
| 2.5 | 250 | 36.3 |
| 3.0 | 300 | 43.5 |
To go from bar to psi, multiply by 14.5038. To go from psi to bar, divide by 14.5038. For kPa, multiply bar by 100.
Where to find the right pressure for your car
The correct pressure is set by the vehicle maker, not by the tire. Look for a placard on the driver's door jamb, inside the fuel filler flap or in the owner's manual. It usually lists front and rear pressures, sometimes with a higher value for a fully loaded car. The number molded on the tire sidewall is the maximum pressure the tire can hold, not the pressure you should use.
Check tires cold
Pressure rises as tires warm up while driving, so the placard values are for cold tires: before driving, or after the car has been parked for a few hours. If you have to check warm tires, do not let air out to reach the cold value.
Gauge pressure vs. absolute pressure
Tire gauges show gauge pressure, the pressure above the surrounding air. A flat tire reads 0 even though the air inside is still at atmospheric pressure (about 1.013 bar or 14.7 psi). This is why converters for tires never add the atmospheric pressure: the values on your placard and your gauge are both gauge pressures.