Pressure Converter
psi, bar, kPa, atmospheres and mmHg for tyres, weather and blood pressure
psi, bar, kPa, atmospheres and mmHg for tyres, weather and blood pressure. No data leaves your browser – every conversion happens locally.
Gauge pressure, weather and medicine
The pascal is the base unit, but it's tiny, so real-world readings use bigger units. One bar is 100 kPa, a millibar is the same as a hectopascal (the unit on weather maps) and one torr is almost exactly one millimetre of mercury.
Tyre and gas-cylinder gauges show gauge pressure, meaning pressure above the surrounding air. A tyre at 32 psi is really at about 46.7 psi absolute. You don't need to adjust for this when converting between gauge readings; just keep both numbers gauge or both absolute.
Common pressure conversions
| 1 atm → Pa | 101,325 Pa |
| 1 bar → Pa | 100,000 Pa |
| 1 psi → Pa | 6,895 Pa |
| 1 atm → psi | 14.696 psi |
| 1 bar → psi | 14.504 psi |
| 1 mmHg → Pa | 133.3 Pa |
Worked examples
Car tyres
32 psi is 2.21 bar or 220.6 kPa. European fuel-flap stickers often list bar, US ones psi.
Blood pressure
120 mmHg (enter it as torr) is 16.0 kPa. Some European medical papers report kPa, everyday monitors stick with mmHg.
Scuba tank
A tank filled to 200 bar holds 2,901 psi, close to the 3,000 psi rating printed on US aluminium tanks.
Tyre pressures in psi, bar and kPa
Door-jamb stickers and pump gauges often use different units, so this is the table to keep in the car. Each row multiplies psi by 6,894.76 to get pascals, then divides into bar and kPa.
| psi | bar | kPa |
|---|---|---|
| 26 psi | 1.79 bar | 179 kPa |
| 28 psi | 1.93 bar | 193 kPa |
| 30 psi | 2.07 bar | 207 kPa |
| 32 psi | 2.21 bar | 221 kPa |
| 35 psi | 2.41 bar | 241 kPa |
| 36 psi | 2.48 bar | 248 kPa |
| 40 psi | 2.76 bar | 276 kPa |
| 44 psi | 3.03 bar | 303 kPa |
Hot tyres and inches of mercury
Tyre figures are cold pressures. After a long drive the air inside warms up and the reading rises, so checking at a highway pump can make an under-inflated tyre look fine. Check after the car has been parked for a few hours, or add a little margin if you can't.
US weather reports and aircraft altimeters use inches of mercury (inHg), which isn't in this tool's list. One inHg is 33.86 hPa, so the standard 29.92 inHg is 1,013.2 hPa. Convert to hPa that way, then use the millibar option here, since 1 hPa equals 1 mbar.