How to use the tyre pressure converter
- Enter the pressure in Value. The default is 32.
- Pick its unit in From: kPa, bar, atm (standard), kgf/cm² (technical atm), psi (lbf/in²) or mmHg (conventional).
- Pick the unit you need in To. The answer appears at once, with the same pressure in all six units below it.
- Scroll down for the Common tyre pressures table, which lists 26 to 100 psi in bar and kPa.
What it does and when to use it
Tyre pressure is printed in different units depending on where a car or bike was sold. A US placard says 35 psi, a European one says 2.4 bar, and a Japanese or Canadian manual may give 240 kPa. Petrol station air machines and cheap gauges often show only one of these. This tool turns the number you have into the number your pump understands.
It also works for bicycle tyres (road bikes often run 80–100 psi, shown in the table), air compressors and pressure washer specs. For less common units such as hPa, Torr, inHg or ksi, use the full pressure converter.
How it works
Each unit is stored as a number of pascals. The tool multiplies your value by the From factor and divides by the To factor.
| Unit | Pascals | Definition |
|---|---|---|
| kPa | 1,000 | SI |
| bar | 100,000 | 10⁵ Pa, exact |
| atm (standard) | 101,325 | exact by definition |
| kgf/cm² | 98,066.5 | 1 kgf (9.80665 N) on 1 cm² |
| psi | 6,894.75729317 | 1 lbf on 1 square inch |
| mmHg | 133.322387415 | conventional mercury column |
The psi factor follows from the exact international pound (0.45359237 kg), standard gravity (9.80665 m/s²) and the inch (0.0254 m). NIST lists the same values in Appendix B.8 of its SI guide. Results are shown to 12 significant figures; the tyre table rounds bar to 2 decimals and kPa to whole numbers.
Worked examples
US placard, European pump. 32 psi = 2.20632233381 bar, or 220.6 kPa.
European placard, US gauge. 2.5 bar = 36.2594344326 psi. Set 36 psi.
Canadian manual. 230 kPa = 33.3586796779 psi, the same as 2.3 bar.
Limits and tips
- Check tyres cold. Pressure rises as tyres warm up on a drive, so a hot reading can look a few psi too high. Do not let air out of hot tyres to match the placard.
- mmHg here is the conventional unit (13,595.1 kg/m³ mercury under standard gravity). It differs from the Torr (1/760 atm) by less than one part in a million, so for tyres the two are the same.
- Gauges are rarely better than ±1 psi, so the 12-figure result is more precise than any reading you will take. Round to what your pump shows.
- Planning a long trip on new tyres? The fuel economy converter and the fuel cost calculator help with the rest of the numbers.
Frequently asked questions
What is 32 psi in bar?
My placard says 2.3 bar but my pump shows psi. What do I set?
Is tyre pressure gauge pressure or absolute pressure?
What is kgf/cm² on older gauges?
Should I convert the pressure on the tyre sidewall?
Sources
- NIST Guide to the SI, Appendix B.8: Factors for units listed alphabetically — NIST, accessed 2026-10-08
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