Understanding pressure units
Unit conversion does not change the pressure reference: gauge and absolute pressure are different measurements. A bar is exactly 100,000 Pa; standard atmosphere is 101,325 Pa. Mercury-based values use conventional constants.
Conversion method
For linear units, multiply the input by its factor to the base unit, then divide by the target factor. The table lists definitions where exact and approximate constants where applicable.
| Unit | 1 unit in base units | Definition |
|---|---|---|
| Pascal (Pa) | 1 | Exact definition; display may be rounded |
| Kilopascal (kPa) | 1,000 | Exact definition; display may be rounded |
| Megapascal (MPa) | 1,000,000 | Exact definition; display may be rounded |
| Bar (bar) | 100,000 | Exact definition; display may be rounded |
| Millibar (mbar) | 100 | Exact definition; display may be rounded |
| Pound per square inch (psi) | 6,894.757293168 | Approximate / conventional value |
| Kilopound per square inch (ksi) | 6,894,757.293168 | Approximate / conventional value |
| Standard atmosphere (atm) | 101,325 | Exact definition; display may be rounded |
| Torr (Torr) | 133.3223684211 | Exact definition; display may be rounded |
| Millimeter of mercury (mmHg) | 133.322387415 | Approximate / conventional value |
| Inch of mercury (inHg) | 3,386.389 | Approximate / conventional value |
Worked example and common conversions
10 psi = 0.6894757293 bar. Keep full precision during conversion, then round the final result to the precision of your measurement.
| From | To |
|---|---|
| 10 psi | 0.6894757293 bar |
| 10 bar | 145.0377377302 psi |
| 10 kPa | 1.4503773773 psi |
| 10 atm | 1,013,250 Pa |
| 10 mmHg | 1.3332238742 kPa |
| 10 psi | 68.9475729317 kPa |