Where each pressure unit is used
- Pascal (Pa) is the SI unit. Kilopascals (kPa) appear on tire placards in many countries.
- Bar is 100 kPa, close to the air pressure at sea level. Used for tires, bikes, diving and espresso machines in Europe.
- psi (pounds per square inch) is used for tires and tools in the US.
- Hectopascal (hPa) equals the millibar (mbar) and is the standard unit for air pressure in weather reports. Normal air pressure is 1013.25 hPa.
- mmHg and inHg come from mercury barometers. Blood pressure is measured in mmHg, and US weather and aviation use inHg.
- Atmosphere (atm) is the standard air pressure at sea level, 101,325 Pa.
Tire and tank gauges show gauge pressure, the pressure above the surrounding air. Absolute pressure adds about 1 bar (14.7 psi). Convert gauge to gauge and absolute to absolute.
Common pressure conversions
| From | Equals |
|---|---|
| 1 bar | 14.50377377 pounds per square inch |
| 1 pound per square inch | 0.06894757293 bar |
| 1 pound per square inch | 6.894757293 kilopascals |
| 1 atmosphere | 1,013.25 hectopascals |
| 1 atmosphere | 14.69594878 pounds per square inch |
| 1 millimeter of mercury | 0.1333223874 kilopascals |
| 1 inch of mercury | 33.86389 hectopascals |
Tire pressure: psi to bar
| Pounds per square inch (psi) | Bar (bar) |
|---|---|
| 26 | 1.79 |
| 28 | 1.93 |
| 30 | 2.07 |
| 32 | 2.21 |
| 33 | 2.28 |
| 34 | 2.34 |
| 35 | 2.41 |
| 36 | 2.48 |
| 38 | 2.62 |
| 40 | 2.76 |
| 44 | 3.03 |
| 50 | 3.45 |
| 60 | 4.14 |
How to use it
- 1Pick the unit you have on the left and the unit you want on the right.
- 2Type a value on either side. The other side updates as you type, and the swap button turns the conversion around.
- 3Read the result and the factor below it, or tap any unit in the list to convert into it. Copy the result or a link to share it.
Frequently asked questions
How many psi is 2.5 bar?
About 36.3 psi. One bar is about 14.5 psi, so multiply bar by 14.5 for a quick estimate.
Is a bar the same as an atmosphere?
Almost. One atmosphere is 1.01325 bar, so the two differ by about 1.3 percent.
Are hPa and mbar the same?
Yes. One hectopascal equals one millibar, so weather reports can use either.
Should I convert gauge or absolute pressure?
Convert like with like. Tire pressure is gauge pressure; if a spec gives absolute pressure, subtract about 1 bar or 14.7 psi first.