- Use the placard on the driver’s door edge, not the maximum printed on the sidewall.
- Measure cold: parked for about three hours, or driven less than about 2 km.
- Underinflation heats the sidewall. Overinflation shrinks the contact patch. Do not pass the sidewall maximum.
- This page only converts units. It does not know your vehicle or its load.
How it works
Tire placards mix three units. A US door sticker often says 32 psi, a European placard says 2.2 bar or 220 kPa, and a gauge may show only one of them. This page converts psi, bar, and kilopascals with the definitions of those units, not with a rounded “1 bar ≈ 15 psi” shortcut. It does not know your car, the load in the trunk, or whether the tire is hot. Read the number, then use the placard on the vehicle.
One pound-force is the international pound, 0.45359237 kg, times standard gravity, 9.80665 m/s², which is 4.4482216152605 newtons. One inch is 0.0254 m, so one square inch is 0.00064516 m². One psi is that force divided by that area: 6894.757293168361 pascals. One bar is 100000 pascals exactly, and one kilopascal is 1000 pascals, so 1 bar = 100 kPa with nothing left over. The page divides by those factors. Psi is shown to two decimal places, bar to three, and kPa to one.
What 32 psi and 2.2 bar actually are
32 psi is 220.632233381 kPa, shown as 220.6 kPa, and 2.206322334 bar, shown as 2.206 bar. The familiar “32 psi = 2.2 bar” placard pair is a rounding, not an identity. 2.2 bar is exactly 220 kPa and 31.908 psi, shown as 31.91 psi. If you set a gauge to 2.2 bar you are about 0.09 psi under 32. That is smaller than most gauges can repeat. It is still a different number, and the page will not hide it.
2.5 bar is exactly 250 kPa and 36.259434 psi, shown as 36.26 psi. A sidewall that says “maximum 44 psi” is 3.033 bar and 303.4 kPa. That sidewall figure is a tire limit, not the pressure the car was designed to run. The placard on the driver’s door edge, or the fuel-filler door on some cars, is the number to match. It can differ between front and rear, and it can change when the car is loaded.
Short safety notes
Measure cold. The usual meaning is that the car has been parked for about three hours, or has been driven less than about 2 km. A hot tire reads higher because the air inside expanded. Bleeding a hot tire down to the placard leaves it under the placard once it cools. Underinflation flexes the sidewall, builds heat, and wears the shoulders. Overinflation shrinks the contact patch and wears the center. Do not inflate past the maximum molded on the sidewall.
A TPMS light is not a gauge. Many systems warn only after a large drop, on the order of a quarter of the placard pressure, and they do not tell you the spare. This page does not talk to a sensor, does not adjust for altitude, and does not replace the load table in the owner’s manual. Nitrogen, compressed air, and a bicycle pump are the same conversion: the unit is a pressure, not a gas.
Worked examples
Input: 32 psi
Output: 2.206 bar and 220.6 kPa
Input: 2.2 bar
Output: 220 kPa exactly, and 31.91 psi
Input: 2.5 bar, or 250 kPa
Output: 36.26 psi
Limits
- The display rounds. 32 psi is 2.206322334 bar before it is cut to three decimals. Typing the rounded 2.206 bar back in lands within 0.01 psi of 32.
- kgf/cm² is not a field. It is close to the bar (1 kgf/cm² = 0.980665 bar) and is not the same number.
- Nothing here looks up a vehicle. Two cars can both wear a 205/55R16 tire and ask for different pressures.
Common mistakes
- Setting the sidewall maximum because it is printed in larger type than the door placard.
- Letting air out of a hot tire until the gauge matches the cold placard.
- Treating 1 bar as 15 psi. One bar is 14.5038 psi. At 2.5 bar the shortcut is already about 1.2 psi high.
Questions
Is 220 kPa the same as 32 psi?▾
Does the page use the approximate 14.5 psi per bar?▾
Can I use this for a shock absorber or a compressor tank?▾
Sources
- Pound-force: 0.45359237 kg × 9.80665 m/s². Inch: 0.0254 m exactly. Psi follows from those two definitions.
- 1 bar = 100000 Pa exactly. 1 kPa = 1000 Pa exactly.