# Tyre Pressure Units PSI to Bar to kPa – Conversion Chart

Have you ever wondered why tyre pressure is not measured the same way around the world? There are three different types of measurements used around the world for tyre pressure, from PSI to Bar to kPa. To find out more about these tyre pressure measure systems, read on and find out how to convert from one to the others whenever needed.

Checkout our Tyre Pressure Charts for popular car models.

## History and Meaning of kPa

The kPa equals to 1000 Pascals and it is a metric unit used to measure pressure. Pascals owe their name to Blaise Pascal, a French scientist who was particularly interested in measuring the strength needed in diverse hydraulic systems. Pascals are quite a small unit mostly used to measure low pressure environments, and that’s why tyre pressure is commonly measured in kPa in countries which follow the metric system (think kilometres and kilograms instead of miles and pounds).

It is commonly used in most of Europe, except for Britain where the imperial system is way more commonly used. It is widely accepted as more reputable than the Bar, for reasons which we will discuss in further detail along this article.
In mathematics and science, the Pascals and kPa are well more used than Bars, however, in countries which use the imperial system, kPa are converted to PSI.

Pascals measure pressure by unit area, and since Newtons (which get their name from Sir Isaac Newton) measure applied strength for the metric system, both are often correlated. A Pascal means one Newton per square meter.

The Pascal is still the most commonly used means of measurement for pressure in scientific contexts, even in countries which use the imperial system, so scientists often have to convert PSI to Pascals. This results from its invention coming from a well-known scientist, so it is a given in the scientific community that when you are talking about pressure in an article, youâ€™ll measure it in Pascals.

## History and Meaning of Bar

Bars are also related to Pascals, in that a Bar equals to one hundred thousand Pascals. Bars were firstly invented as a measure means by the Norwegian meteorologist Vilhelm Bjerknes. It is a metric unit of pressure, and it’s most commonly used in weather forecasting (since Bjerknes is considered to be the founding father of modern weather forecasting). However, due to the bad reputation meteorology gets as a science, Bars are not commonly used in science. Its name derives from the Greek word baros, which means weight. The Bar is a metric measure unit, however, it is not conventionally accepted by the International System of Units (SI), which regulates metric system units.

Since Pascals are a quite small unit, milibars are more commonly used for weather forecasting to measure atmospheric pressure. A milibar equals to 101.325 kPa. For convenience, milibars are used in meteorology since Pascals would return much larger values, which are difficult to deal with when talking about weather forecasting. Milibars solve this issue and even though they are not accepted within the International System of Units, they are still used commonly around most of the world. This includes Europe and most Asian countries, which are known to use the metric system as well.

## History and Meaning of PSI

A PSI translates to a pound-force per square inch, and is the most commonly used pressure unit among countries which use the imperial system, like the United States of America, Britain (where the imperial system was first implemented) and other countries like Liberia and Myanmar.

The PSI originates from the avoirdupois pound, which was part of the avoirdupois system that England was known to have used ever since the fourteenth century. Its history begins with the wool trade: an avoirdupois pound was a pound of wool. It was only in 1959 that the avoirdupois pound was standardised and became a unit used around the world for the imperial system. The avoirdupois was the predecessor of the common known pound that is still used in the modern world for the imperial system, which can be a headache if you have to convert PSI to kPa or Bars. This happens especially when you live in a country that uses the imperial system, like the United States, and you buy a car from Europe that is not standardised to imperial measurement units.

Either kPa, PSI or Bar can be used to measure tyre pressure depending on the country, so it is a nightmare for amateur mechanics (and some professionals as well if they are only used to one type of measurement, be it according to the metric or the imperial system). If you ever need to make that type of conversion, read on to figure out the formulas used.

## How to convert Bars to PSI

If you’re using a car that uses bars to measure its tyre pressure, you have to know that one bar equals to 14.503773773 PSI. This makes for quite difficult calculations to do if you want to be precise. Let’s say you have a car that needs 2.5 bar of tyre pressure and you need to know how much that means in PSI.

So you multiply 2.5 per 14.503773773 and you get approximately 36,26 PSI. This is an average tyre pressure requirement, but all cars have different tyre pressure requirements to keep your tyres running for a longer time.

## How to convert PSI to Bars

If, on the other hand, you’re from a country that uses the metric system and you just got an American car, you have to do the opposite math – convert PSI to Bars. One PSI equals to 0.0689475729 Bar, so if you have a car that requires 30 PSI for tyre pressure you multiply thirty per 0.0689475729 and you get around 2.07 Bars.

## How to convert PSI to kPa

Now that you know that one Bar equals to 100000 Pascals, and one kPa equals to 1000 Pascals, the math is a bit easier on this one. To know the exact tyre pressure in kPa, you get the 30 PSI from the example above and you multiply them by 0.0689475729, just like before – except this time you’ll have to multiply the 2.07 per one hundred, which gives you 207 kPa in tyre pressure. Not so difficult anymore, is it?

Remember that you should always check your car manual to figure out the required tyre pressure for the specific brand and model you have. Now that you know how to convert between Bars, PSI and kPa, you’ll be able to set the exact tyre pressure your new car needs no matter the measurement your tools are in.

PSIBARKPA
10.0686.8
20.1313
30.2020
40.2727
50.3434
60.4141
70.4848
80.5555
90.6262
100.6868
110.7575
120.8282
130.8989
140.9696
151.03103
161.10110
171.17117
181.24124
191.31131
201.37137
211.44144
221.51151
231.58158
241.65165
251.72172
261.79179
271.86186
281.93193
291.99199
302.06206
312.13213
322.20220
332.27227
342.34234
352.41241
362.48248
372.55255
382.62262
392.68268
402.75275
412.82282
422.89289
432.96296
443.03303
453.10310
463.17317
473.24324
483.30330
493.37337
503.44344
513.51351
523.58358
533.65365
543.72372
553.79379
563.86386
573.93393
583.99399
594.06406
604.13413
614.20420
624.27427
634.34434
644.41441
654.48448
664.55455
674.61461
684.68468
694.75475
704.82482
714.89489
724.96496
735.03503
745.10510
755.17517
765.24524
775.30530
785.37537
795.44544
805.51551
815.58558
825.65565
835.72572
845.79579
855.86586
865.92592
875.99599
886.06606
896.13613
906.20620
916.27627
926.34634
936.41641
946.48648
956.55655
966.61661
976.68668
986.75675
996.82682
1006.89689