Car & Vehicle

Tyre Pressure Converter

Convert tyre pressure between psi, bar, kPa and kg/cm², exactly.

4 inputs Free, no sign-up

Your figures

The reading on the gauge or the figure on the placard.

Optional. Roughly what the pressure becomes if the tyre warms or cools by this much - useful when the placard figure is a cold one and the tyre is not.

Try an example

Result

Your result

Enter your figures and the result appears here.

Estimates only. Rates, fees and specifications change. Confirm against the official source before you rely on a figure — see our disclaimer.

About this calculator

Four units are in daily use for tyre pressure and they are nowhere near each other. 32 psi is 2.21 bar, 220.6 kPa and 2.25 kg/cm². A placard reading in psi taken onto a gauge reading in bar is a tyre at a seventh of its pressure; the mistake the other way is a tyre at seven times it.

This is the conversion worth getting exactly right, so it uses exact definitions rather than rounded constants.

How to use this calculator

  1. Enter the pressure you have.
  2. Say which unit it is in — the placard, the handbook or the gauge will say.
  3. Pick the unit your gauge or compressor uses.

All four are shown regardless.

The formula

1 bar     = 100 kPa exactly
1 psi     = 6.894757293168361 kPa exactly
1 kg/cm²  = 98.0665 kPa exactly

All three are definitions rather than measurements, so the conversion is exact. Everything is converted through kilopascals, which means no pair of units needs its own factor and no two pairs can disagree.

The temperature option uses the gas law on absolute pressure: the atmosphere is added before the ratio and taken off afterwards. Scaling the gauge reading directly overstates the change by about 40%.

SymbolMeaningUnit
Pressure Gauge pressure psi, bar, kPa, kg/cm²
Temperature Change in tyre temperature °C

Worked example

32 psi, converted:

bar      2.206
kPa      220.632
kg/cm²   2.250

Warm the tyre by 15 °C and the same tyre reads about 34.4 psi — which is why a tyre checked after a drive appears over-inflated.

Notes and limits

  • This page converts a pressure. It does not recommend one. The correct figure for your vehicle is on the placard in the driver's door frame or in the handbook, differs between front and rear, and goes up when the car is loaded.
  • Placard pressures are cold pressures — measured before driving, or after the car has stood a few hours. A tyre checked warm reads several psi high, and letting that air out leaves it under-inflated once it cools.
  • kg/cm² appears on older gauges and compressors and is within 2% of bar, which is why the two get used interchangeably and why the difference is worth seeing.
  • Under-inflation wears the shoulders, raises fuel consumption and is the main cause of heat-related tyre failure. Over-inflation wears the centre and reduces grip.
  • Check monthly and before a long trip. Tyres lose pressure slowly even when nothing is wrong.

What this calculation assumes

  • All conversions are exact by definition.
  • Pressures are gauge pressures - what a gauge reads above the surrounding air.
  • The temperature estimate assumes a fixed volume and a 20 °C starting point. Real tyres also flex and heat unevenly.
  • No pressure is recommended for any vehicle.

Frequently asked questions

How many psi is 2.2 bar?

31.9 psi. A bar is 100 kPa and a psi is 6.894757 kPa, so one bar is about 14.5 psi.

What tyre pressure should I use?

The one on the placard in your driver's door frame, or in the handbook. It differs between the front and rear axles and there is usually a higher figure for a fully loaded car. This page will not suggest a number, because the right one depends on the vehicle.

Why does my tyre read higher after driving?

The air inside warms up and expands. A rise of 15 °C adds roughly 2.4 psi to a tyre at 32. Placard figures are cold figures, so checking warm and bleeding air down to the placard number leaves the tyre under-inflated.

Is kg/cm² the same as bar?

Close but not identical - one kg/cm² is 0.980665 bar, about 2% lower. For tyre pressures the difference is under half a psi, which is why the two are often treated as interchangeable.

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