Pressure Converter
Enter a pressure in any unit and get the rest instantly — pascals, kilopascals, bar, PSI, and atmospheres, converted with exact constants, not rounded approximations.
All five units at once
| Unit | Value |
|---|---|
| Pascals (Pa) | — |
| Kilopascals (kPa) | — |
| Bar | — |
| PSI (lb/in²) | — |
| Atmospheres (atm) | — |
Exact constants, not rounded ones
Pascals (Pa) are the SI base unit — everything else here is defined in terms of them. A kilopascal is exactly 1,000 Pa and a bar is exactly 100,000 Pa by simple metric scaling, but PSI and the standard atmosphere are legal definitions, not measurements: 1 psi is defined as exactly 6894.757293168 Pa (from the pound-force and square-inch definitions), and 1 atm is defined as exactly 101,325 Pa. Because this tool uses those exact defining constants instead of rounded textbook figures, the results are as precise as floating-point arithmetic allows, not an approximation stacked on an approximation.
Worked example
Standard sea-level atmospheric pressure — 1 atmosphere — is a useful, checkable reference point: 1 atm = 101,325 Pa = 101.325 kPa ≈ 1.01325 bar ≈ 14.6959 psi. That's exactly what this tool shows as its starting values above, so you can confirm it against any reference table you trust. Switch the "From" unit to psi and enter 32 — the everyday tire-pressure number — and the bar column reads about 2.2069, kPa about 220.69: a good sanity check that the conversion math lines up with what a tire gauge would show you in either unit.
Frequently asked questions
Why is 1 atmosphere exactly 101,325 Pa?
Because that's its legal definition, not a measurement. "Standard atmosphere" was fixed at exactly 101,325 pascals by international agreement (tied to the old definition of 760 mmHg at 0°C and standard gravity) so that everyone doing physics or engineering uses the same reference value for sea-level air pressure. It isn't an average or an approximation — it's a defined constant, the same way a kilometer is defined as exactly 1,000 meters.
What's the difference between PSI and bar, and why do both exist?
They're two unrelated measurement traditions that both stuck: PSI (pounds-force per square inch) comes from the US customary system and is standard on American tire gauges and plumbing fittings; bar comes from the metric world (1 bar is close to, but not the same as, 1 atmosphere) and dominates in Europe. 1 bar ≈ 14.5038 psi. Neither is more "correct" — which one you'll see mostly depends on which country made your gauge.
My tire says 32 PSI — what's that in bar or kPa?
32 psi converts to about 2.2069 bar, or 220.69 kPa. Car tire pressures typically run 28–36 psi (1.9–2.5 bar); bicycle tires run much higher, often 80–130 psi (5.5–9 bar) for road bikes. Always check the number molded into the tire sidewall or your vehicle's door-jamb sticker rather than a generic rule of thumb — it varies by tire size and load.
What about millibars or hPa, which I see in weather reports?
A hectopascal (hPa) is exactly 100 pascals, and a millibar (mbar) is defined to be numerically identical to a hectopascal — so 1013.25 hPa (a typical sea-level weather reading) equals 1013.25 mbar equals 101.325 kPa, which is exactly 1 atmosphere. Meteorology just prefers hPa/mbar as a unit scaled conveniently for everyday air-pressure numbers; you can get there from this tool by reading the kPa row and multiplying by 10.
Is my input sent anywhere?
No. Every conversion runs with plain JavaScript arithmetic in your browser the moment you type — nothing you enter is transmitted, logged, or stored on a server.