Pressure Converter
Convert pascals, bar, psi, atmospheres and mmHg.
Convert between common pressure units used in weather, engineering, tires and diving. Enter a value and pick the units — everything is converted through pascals (the SI base unit) for accuracy.
Formula / method
Examples
14.504 psi
101.325 kPa
The SI unit and everyday units
Pressure is force spread over an area, and the SI unit is the pascal (Pa), equal to one newton per square meter. A pascal is tiny, so practical units are larger: 1 bar = 100,000 Pa = 100 kPa, which is close to normal air pressure. The standard atmosphere is defined as exactly 101,325 Pa, so 1 atm is about 1.013 bar or 760 mmHg.
psi, mmHg and gauge vs absolute
The pound per square inch (psi) is common in the US for tire and plumbing pressure; 1 psi is about 6,894.76 Pa, and 1 atm is roughly 14.696 psi. The millimeter of mercury (mmHg, or torr) is used for blood pressure and vacuum work, with 1 mmHg equal to about 133.322 Pa.
A frequent source of confusion is gauge versus absolute pressure. A tire gauge reads pressure above the surrounding air, so a tire at 32 psi gauge is actually about 46.7 psi absolute. This converter treats the numbers you enter as-is, so add atmospheric pressure yourself if you need absolute values.
Where it's used
- Converting a tire pressure between bar and psi
- Reading a weather barometer in hPa or millibars versus inches of mercury
- Converting a scuba tank or regulator rating between bar and psi
- Engineering calculations that need SI pascals or kilopascals
- Interpreting a blood-pressure reading given in mmHg
Real-world examples
- 1 bar converts to about 14.5 psi, close to a typical car tire pressure
- Standard sea-level atmosphere is 1 atm = 101.325 kPa = 760 mmHg = 14.696 psi
- A tire inflated to 32 psi is about 2.2 bar
A bit of history
The pascal, the SI unit of pressure equal to one newton per square metre, is named after French mathematician and physicist Blaise Pascal and was formally adopted by the 14th General Conference on Weights and Measures in 1971.
Did you know?
The 'torr', another name for the millimetre of mercury, honours Evangelista Torricelli, the Italian physicist who invented the mercury barometer in 1643.
FAQ
What is normal atmospheric pressure?
Sea-level air is about 1 atm = 101,325 Pa = 1.01325 bar = 14.696 psi.