To convert psi to bar, multiply by 0.0689476, or divide by 14.5038. So 32 psi is 2.21 bar and 35 psi is 2.41 bar. For the reverse, multiply bar by 14.5038: 2.5 bar is 36.3 psi. For kilopascals, multiply psi by 6.895.
Where do the psi and bar factors come from? #
The bar is a metric unit set at exactly 100,000 pascals (NIST SP 811 lists it as exact). It was chosen because it’s close to atmospheric pressure at sea level.
psi means pound-force per square inch: the force of one pound under standard gravity (9.80665 m/s²), spread over a square inch. Working it through from the exact pound and inch definitions gives 6,894.757 Pa. Divide by 100,000 and one psi is 0.0689476 bar.
The mental shortcut #
psi to bar: divide by 14.5. That’s accurate to better than 0.1%. If 14.5 is awkward, multiply by 0.07: 32 × 0.07 = 2.24 bar (exact: 2.21), about 1.5% high.
bar to psi: multiply by 14.5. For a rougher version, multiply by 15 and subtract a little. 2.2 bar × 15 = 33, and the exact answer is 31.9.
Car tire pressure chart: psi to bar and kPa #
| psi | bar | kPa |
|---|---|---|
| 26 | 1.79 | 179 |
| 28 | 1.93 | 193 |
| 30 | 2.07 | 207 |
| 32 | 2.21 | 221 |
| 33 | 2.28 | 228 |
| 35 | 2.41 | 241 |
| 36 | 2.48 | 248 |
| 38 | 2.62 | 262 |
| 40 | 2.76 | 276 |
| 42 | 2.90 | 290 |
| 44 | 3.03 | 303 |
| 50 | 3.45 | 345 |
bar to psi chart #
| bar | psi | Where you’ll see it |
|---|---|---|
| 1.0 | 14.5 | about atmospheric pressure |
| 1.8 | 26.1 | low end for car tires |
| 2.0 | 29.0 | car tires |
| 2.2 | 31.9 | car tires |
| 2.4 | 34.8 | car tires |
| 2.5 | 36.3 | car tires |
| 2.8 | 40.6 | loaded car or SUV tires |
| 3.0 | 43.5 | light truck tires |
| 3.5 | 50.8 | light truck tires |
| 4.0 | 58.0 | wide bicycle tires |
| 6.0 | 87.0 | road bike tires |
| 8.0 | 116.0 | road bike tires, air compressors |
| 10 | 145.0 | pressure washers (low end) |
| 200 | 2,900.8 | scuba cylinders |
These are examples of where each value turns up, not recommendations. Your vehicle’s correct pressure is the one its manufacturer specifies.
Which pressure should your tires be? #
Use the pressure on your vehicle’s tire placard, usually on the driver’s door jamb, or in the owner’s manual. It may be listed in psi, in kPa, or in both. Check it when the tires are cold, before you’ve driven far, because driving warms the air and raises the reading. The large number molded into the tire sidewall is the tire’s maximum pressure, not the one to inflate to.
If your car’s manual is European and lists bar, convert it with the chart above or multiply by 14.5. A front-axle figure of 2.3 bar is 33.4 psi.
What’s the difference between gauge and absolute pressure? #
A tire gauge reads gauge pressure, the pressure above the surrounding air. A flat tire reads 0 on a gauge, even though the air inside is still at atmospheric pressure. Engineers sometimes write this as psig.
Absolute pressure counts from a perfect vacuum. It’s gauge pressure plus atmospheric pressure, about 14.7 psi or 1.013 bar at sea level. Weather reports and scuba tables use absolute pressure, while tire and compressor gauges use gauge pressure. Unless a spec says “absolute” or “psia,” assume gauge.
How do bar, atm, kPa and mmHg compare? #
| Unit | Equals in psi | Equals in bar |
|---|---|---|
| 1 psi | 1 | 0.0689 |
| 1 bar | 14.504 | 1 |
| 1 standard atmosphere (atm) | 14.696 | 1.01325 |
| 1 kPa | 0.145 | 0.01 |
| 1 mbar (hPa) | 0.0145 | 0.001 |
A bar and an atmosphere are close but not identical: 1 atm is exactly 101,325 Pa, or 1.01325 bar. Weather maps use millibars (or hectopascals, the same size), and a typical sea-level reading of around 1,013 mbar is one atmosphere.
Worked examples #
Your bike pump reads 90 psi and the tire sidewall is marked in bar. 90 × 0.0689 = 6.2 bar.
An air compressor is rated at 8 bar. 8 × 14.5 = 116 psi.
An espresso machine advertises 9 bar. 9 × 14.5 = 130.5 psi.
A scuba cylinder is filled to 200 bar. 200 × 14.5038 = 2,901 psi, which is why US cylinders are often quoted around 3,000 psi.
Converting pressure on your phone #
Convert Units Calculator has a Pressure category with pascals, kilopascals, millibar, bar, psi, atmospheres, millimeters of mercury, torr and inches of mercury. Enter 32 with psi selected and bar, kPa and the rest appear together as you type, so a tire placard in any unit is quick to check. It works offline, which is handy at an air pump with no signal.
If pressure is one of several car numbers you’re translating, mpg to L/100km covers fuel economy. The metric to imperial conversion chart has the everyday units in one place, and how to convert units shows how factors like 0.0689 are built.
Frequently asked questions #
What is 32 psi in bar? #
32 psi is 2.21 bar. Multiply 32 by 0.0689476.
What is 2.5 bar in psi? #
2.5 bar is 36.3 psi. Multiply 2.5 by 14.5038.
Is 1 bar equal to atmospheric pressure? #
Almost. Standard atmospheric pressure is 1.01325 bar, about 1.3% more than one bar. Real atmospheric pressure changes with weather and altitude anyway.
How do you convert kPa to psi? #
Divide by 6.895, or multiply by 0.145. So 220 kPa is 31.9 psi, and 250 kPa is 36.3 psi.
What is 30 psi in bar? #
30 psi is 2.07 bar.