Pressure is defined as a force exerted on a surface per unit area. To put it more simply, it’s the force that is put on a certain defined area.
It’s likely you’ll be familiar with the concept in everyday life – for example ‘feeling the pressure’ or ‘applying pressure to a wound’, but when it comes to pressure and tyres, it can be difficult to understand the measurements of pressure, and know where to find them, which is why we’re going to take you through it. There are three commonly used measurements of pressure in tyres – PSI, BAR and kPa, and depending on your vehicle, you may need to convert from one to another.
Your tyre inflation pressure depends on the amount of air that has been pumped into your tyre. It is measured in pounds per square inch (psi), bar or kPa. Your vehicle manufacturer recommends the suitable pressure for your tyres.
PSI is the most common means of measuring tyre pressure in countries that use the imperial system. This includes the USA and UK. PSI stands for ‘pound-force per square inch’ and is an imperial unit of pressure based on avoirdupois units. It is defined as the pressure that results when a force of one pound-force is applied to a one-square-inch area. One psi is approximately 6,895 pascals (N/m2). It can measure everything from blood pressure to tyre pressure.
You will most likely need to convert from BAR or kPa to PSI if you live in a country that uses the imperial system and purchase a car from a country that uses the metric system.
BAR is a metric unit and is most commonly used in weather forecasting to measure atmospheric pressure. I BAR is equal to 14.50 pounds per square inch and is another method used to determine air pressure in tyres, particularly in countries that use the metric system. It is considered a less reliable and less scientific means of measuring pressure than kPa.
The bar and millibar were introduced by the Norwegian meteorologist Vilhelm Bjerknes who founded the modern practice of weather forecasting. The term “bar” comes from the Greek word “baros,” which means weight.
The kPa is a metric unit equal to 1000 Pascals, which take their name from a French scientist called Blaise Pascal, who worked to measure the strength needed in hydraulic systems. As pascals are a relatively small unit, mostly used to measure low pressure environments, tyre pressures are more commonly measured in kPa (kilopascals)
The pascal (Pa) or kilopascal ( kPa ) as a unit of pressure measurement is widely used throughout the world, particularly in countries which follow the metric system. (most of Europe) and in some industries is largely replacing the pounds per square inch (psi) unit. 1 kPa is equal to 0.145038 PSI.
Either kPa, PSI or Bar can be used to measure tyre pressure, and this often depends on where in the world the tyres are manufactured and whether that part of the world uses the metric and imperial system. This can prove tricky for vehicle owners, and even professional, so if you need to make a conversion, here are the formulae you will need:
Converting from BAR to PSI
For an approximate result, multiply the pressure value by 14.504
Converting from PSI to kPa
For an approximate result, divide the pressure value by 6.895
Use the TyreSafe tyre pressure chart below to check and convert your vehicle tyre pressure measurements quickly and easily.
Alternatively, if you want to work out pressures for your specific vehicle, visit one of the following pages:
| PSI | BAR | KPA |
| 1 | 0.068 | 6.8 |
| 2 | 0.13 | 13 |
| 3 | 0.2 | 20 |
| 4 | 0.27 | 27 |
| 5 | 0.34 | 34 |
| 6 | 0.41 | 41 |
| 7 | 0.48 | 48 |
| 8 | 0.55 | 55 |
| 9 | 0.62 | 62 |
| 10 | 0.68 | 68 |
| 11 | 0.75 | 75 |
| 12 | 0.82 | 82 |
| 13 | 0.89 | 89 |
| 14 | 0.96 | 96 |
| 15 | 1.03 | 103 |
| 16 | 1.1 | 110 |
| 17 | 1.17 | 117 |
| 18 | 1.24 | 124 |
| 19 | 1.31 | 131 |
| 20 | 1.37 | 137 |
| PSI | BAR | KPA |
| 21 | 1.44 | 144 |
| 22 | 1.51 | 151 |
| 23 | 1.58 | 158 |
| 24 | 1.65 | 165 |
| 25 | 1.72 | 172 |
| 26 | 1.79 | 179 |
| 27 | 1.86 | 186 |
| 28 | 1.93 | 193 |
| 29 | 1.99 | 199 |
| 30 | 2.06 | 206 |
| 31 | 2.13 | 213 |
| 32 | 2.2 | 220 |
| 33 | 2.27 | 227 |
| 34 | 2.34 | 234 |
| 35 | 2.41 | 241 |
| 36 | 2.48 | 248 |
| 37 | 2.55 | 255 |
| 38 | 2.62 | 262 |
| 39 | 2.68 | 268 |
| 40 | 2.75 | 275 |
| PSI | BAR | KPA |
| 41 | 2.82 | 282 |
| 42 | 2.89 | 289 |
| 43 | 2.96 | 296 |
| 44 | 3.03 | 303 |
| 45 | 3.1 | 310 |
| 46 | 3.17 | 317 |
| 47 | 3.24 | 324 |
| 48 | 3.3 | 330 |
| 49 | 3.37 | 337 |
| 50 | 3.44 | 344 |
| 51 | 3.51 | 351 |
| 52 | 3.58 | 358 |
| 53 | 3.65 | 365 |
| 54 | 3.72 | 372 |
| 55 | 3.79 | 379 |
| 56 | 3.86 | 386 |
| 57 | 3.93 | 393 |
| 58 | 3.99 | 399 |
| 59 | 4.06 | 406 |
| 60 | 4.13 | 413 |
| PSI | BAR | KPA |
| 61 | 4.2 | 420 |
| 62 | 4.27 | 427 |
| 63 | 4.34 | 434 |
| 64 | 4.41 | 441 |
| 65 | 4.48 | 448 |
| 66 | 4.55 | 455 |
| 67 | 4.61 | 461 |
| 68 | 4.68 | 468 |
| 69 | 4.75 | 475 |
| 70 | 4.82 | 482 |
| 71 | 4.89 | 489 |
| 72 | 4.96 | 496 |
| 73 | 5.03 | 503 |
| 74 | 5.1 | 510 |
| 75 | 5.17 | 517 |
| 76 | 5.24 | 524 |
| 77 | 5.3 | 530 |
| 78 | 5.37 | 537 |
| 79 | 5.44 | 544 |
| 80 | 5.51 | 551 |
| PSI | BAR | KPA |
| 81 | 5.58 | 558 |
| 82 | 5.65 | 565 |
| 83 | 5.72 | 572 |
| 84 | 5.79 | 579 |
| 85 | 5.86 | 586 |
| 86 | 5.92 | 592 |
| 87 | 5.99 | 599 |
| 88 | 6.06 | 606 |
| 89 | 6.13 | 613 |
| 90 | 6.2 | 620 |
| 91 | 6.27 | 627 |
| 92 | 6.34 | 634 |
| 93 | 6.41 | 641 |
| 94 | 6.48 | 648 |
| 95 | 6.55 | 655 |
| 96 | 6.61 | 661 |
| 97 | 6.68 | 668 |
| 98 | 6.75 | 675 |
| 99 | 6.82 | 682 |
| 100 | 6.89 | 689 |
First, you need to find the recommended pressures for the tyres. These can be found in several places:
- Your vehicle’s handbook
- Stamped into the sill of the driver’s side door
- Inside the fuel cap
- TyreSafe pressure look-up tools
The recommended pressure is set by the vehicle manufacturer and varies from model to model.
Do be aware that there are different pressures for different vehicle loads – the more passengers or luggage, the higher the pressure will need to be.
Most modern vehicles use a TPMS system to monitor the pressure of your tyres.
The easiest way to check your vehicle tyre pressure is to use an air compressor with a calibrated pressure gauge. These can also be found at most petrol stations.