PSI to Bar Formula
Convert pounds per square inch to bar — divide by 14.5038.
bar = PSI ÷ 14.5038
How it works
Both units measure force spread over an area, so the conversion is a fixed ratio. One pound per square inch is 6,894.757 pascals, and one bar is defined as exactly 100,000 pascals, so 1 psi is 0.0689476 bar and 1 bar is 14.5038 psi. The useful mental anchor is that a bar is very nearly one atmosphere — standard atmospheric pressure is 101,325 Pa, which is 1.01325 bar or 14.6959 psi — because the bar was sized that way deliberately when it was introduced in 1909. The most common place this conversion goes wrong is tyre pressures, where the two units are close enough in everyday magnitude to be confused and far enough apart to matter: a 32 psi tyre is 2.21 bar, and a car specified at 2.2 bar wants 31.9 psi, not 2.2 psi. The second thing to check is whether a figure is gauge or absolute pressure. Tyre gauges, hydraulic systems and most industrial instruments read gauge pressure, meaning pressure above the surrounding atmosphere, so a gauge showing zero is really sitting at about one bar. Absolute pressure adds that atmosphere back, and mixing the two produces an error of roughly 14.7 psi.
Variables
- barPressure in bar (result)
- PSIPressure in pounds per square inch (input)
Worked examples
| Input | Result |
|---|---|
| 30 PSI | ≈ 2.07 bar (typical car tire) |
| 100 PSI | ≈ 6.89 bar (bike tire) |
| 14.5038 PSI | = 1.00 bar (sea-level atmosphere) |
Practical applications
- Setting tyre pressures from a manual written in the other unit
- Comparing hydraulic or pneumatic equipment specified in different markets
- Reading dive-cylinder and regulator pressures, which are almost always in bar
- Interpreting boiler, compressor and pipeline ratings across US and European documentation
Common mistakes
- Treating the numbers as interchangeable on tyres. 2.2 bar is 31.9 psi; entering 2.2 psi would leave the tyre effectively flat.
- Mixing gauge and absolute pressure. They differ by about one atmosphere, or 14.7 psi.
- Assuming 1 bar is exactly one atmosphere. It is 1.01325 atmospheres — close, but not the same.
- Confusing bar with millibar in weather reports. Atmospheric pressure is quoted around 1,013 mbar, which is just over one bar.
Used in
Use it in a tool
FAQs
Why is the divisor 14.5038?+
Because 1 bar = 100,000 Pa and 1 PSI = 6,894.76 Pa, so 100,000 ÷ 6,894.76 ≈ 14.5038.
Is bar the same as atmosphere?+
Close — 1 atm = 1.01325 bar. For most engineering work the difference is ignored.