What this calculator does
Turn a pressure in psi into bar, or bar into psi, in one step. PSI (pounds-force per square inch) is the pressure unit printed on US tire sidewalls, air compressors, pressure washers and bike pumps. The bar is its metric partner. You'll see it on European tire placards (the pressure label), scuba tanks, espresso machines and hydraulic equipment. Many gauges show both scales, but a spec sheet or a manual usually gives only one.
One bar is set at exactly 100,000 pascals (Pa, the metric unit of pressure). That's close to, but slightly less than, average air pressure at sea level. One psi is the weight of one pound under standard gravity, spread over one square inch. That works out to 0.45359237 kg × 9.80665 m/s² ÷ (0.0254 m)² ≈ 6,894.757 Pa. So 1 bar ≈ 14.5038 psi, and 1 psi ≈ 0.0689 bar.
Where it's used
Why this math matters outside the classroom:
- Imported tire gauges. A tire gauge reading 2.4 bar shows the same pressure as about 34.8 psi.
- Scuba tanks. A tank filled to 3,000 psi holds air at about 207 bar.
- Pressure washers. A 2,000 psi pressure washer works at about 138 bar.
- Bike pumps. A road bike pumped to 7 bar is at about 101.5 psi.
- Air compressors. A compressor that cuts out at 150 psi reaches about 10.3 bar.
Grade level and standards: Grades 6–7; Common Core State Standards for Mathematics 6.RP.A.3.d. © Copyright 2010. National Governors Association Center for Best Practices and Council of Chief State School Officers. All rights reserved.
How to use it
- Enter a pressure in psi or bar.
- Choose psi to bar, or bar to psi.
- Read the result and the working. The table lists common tire, compressor and tank pressures for the direction you chose.
What the inputs mean
- Value to convert
- A pressure in psi (for psi → bar) or bar (for bar → psi). Use the same kind of reading on both sides: gauge or absolute (explained below).
- Direction
- Which way to convert.
Formula and method
bar = psi × 6,894.757293168 ÷ 100,000 ≈ psi × 0.0689475729317 psi = bar × 100,000 ÷ 6,894.757293168 ≈ bar × 14.503773773
Here 6,894.757293168 is the number of pascals in one psi, and 100,000 is the number of pascals in one bar. Neither factor is a short decimal, because the psi depends on the pound, the inch and standard gravity together. The calculator keeps full precision. It shows the factor to 12 significant figures (12 digits).
Both units measure the same thing: force spread over an area. So the conversion is a single multiplication, with nothing to add or subtract.
Worked example
A tire placard in psi says 32. What is that in bar?
- The conversion factor, to 12 significant figures: 1 psi ≈ 0.0689475729317 bar.
- Multiply: 32 × 0.0689475729317 = 2.20632233381.
Result: 32 psi is about 2.21 bar.
Understanding the result
Here's a shortcut you can do in your head. Divide psi by 14.5 to get bar, or multiply bar by 14.5 to get psi. The error is about 0.03%, smaller than any tire gauge can show. Dividing by 15 is quicker, but it reads about 3% low.
Some useful values: standard air pressure at sea level is 14.696 psi, which is 1.01325 bar. Scuba tanks are often filled to around 200 bar in metric countries (about 2,900.8 psi). In the US they're often filled to 3,000 psi (about 206.8 bar). For your own tires, use the figure on the label inside the driver's door frame. Don't use the maximum molded on the sidewall.
The most common mistake is mixing up gauge and absolute pressure. A tire gauge reads pressure above the surrounding air (psig, or bar(g)). A flat tire reads 0, even though the air inside is at about 14.7 psi absolute (psia). Convert gauge to gauge and absolute to absolute. Never mix them.
Assumptions and limitations
- psi means pound-force per square inch, under standard gravity (9.80665 m/s²).
- Input and output are the same kind of pressure (both gauge or both absolute).
- The converter doesn't add or remove the pressure of the surrounding air. To go from psig to psia, add the local air pressure yourself.
- Tire pressure rises as tires warm up. Compare readings taken when the tires are cold.
Frequently asked questions
How many psi is 1 bar?
About 14.5037737730 psi.
Is 1 bar the same as 1 atmosphere?
Nearly. One standard atmosphere (average air pressure at sea level) is 1.01325 bar. So 1 bar is about 1.3% less than average sea-level air pressure.
What do psig and psia mean?
psig is gauge pressure, measured above the surrounding air. psia is absolute pressure, measured from a perfect vacuum (no air at all). At sea level, psia ≈ psig + 14.7.
Why do European tire charts use bar while US charts use psi?
Each market just uses its own usual unit. The pressures themselves are the same: 2.2 bar and 32 psi describe almost the same tire inflation.
How this calculator is checked
Method: 1 bar = 100,000 Pa (exact); 1 psi = 0.45359237 kg × 9.80665 m/s² ÷ (0.0254 m)² = 6,894.757293168… Pa. The calculation is covered by automated tests with known reference values and edge cases. Last updated 2026-10-18. Found a problem? Tell us.
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