How this conversion works
Pressure is force per unit area, and the SI unit is the pascal (one newton per square meter). One bar is exactly 100,000 Pa, and the standard atmosphere is defined as exactly 101,325 Pa.
One psi is the force of one pound (0.45359237 kg × standard gravity 9.80665 m/s²) on one square inch, which equals about 6,894.757 Pa. Mercury-column units use conventional fixed values.
Formula: result = value × (base units per source unit) ÷ (base units per target unit)
Where this conversion is used
- Tire pressure on gauges in psi, bar or kPa.
- Weather barometric pressure in hPa (mbar) or inches of mercury.
- Blood pressure readings in mmHg.
- Compressor, pump and scuba equipment specifications.
Worked example: 32 psi tire pressure to bar and kPa
- One psi ≈ 6,894.757 Pa.
- 32 × 6,894.757 = 220,632.2 Pa = 220.63 kPa.
- Divide by 100,000 Pa per bar: about 2.206 bar.
Unit definitions
| Unit | In pascals | Note |
|---|---|---|
| Pascal (Pa) | 1 | |
| Kilopascal (kPa) | 1,000 | |
| Megapascal (MPa) | 1,000,000 | |
| Bar (bar) | 100,000 | |
| Millibar (mbar) | 100 | |
| Pound per square inch (psi) | 6,894.75729317 | |
| Standard atmosphere (atm) | 101,325 | 101,325 Pa exactly. |
| Torr (Torr) | 133.322368421 | |
| Millimeter of mercury (mmHg) | 133.322387415 | Conventional value, 133.322387415 Pa. |
| Inch of mercury (inHg) | 3,386.389 | Conventional value at 0 °C. |
Pounds per square inch to bars
| Pound per square inch (psi) | Bar (bar) |
|---|---|
| 1 | 0.0689 |
| 10 | 0.6895 |
| 15 | 1.0342 |
| 30 | 2.0684 |
| 32 | 2.2063 |
| 35 | 2.4132 |
| 50 | 3.4474 |
| 100 | 6.8948 |
| 150 | 10.3421 |
Bars to pounds per square inch
| Bar (bar) | Pound per square inch (psi) |
|---|---|
| 0.5 | 7.2519 |
| 1 | 14.5038 |
| 1.5 | 21.7557 |
| 2 | 29.0075 |
| 2.5 | 36.2594 |
| 3 | 43.5113 |
| 5 | 72.5189 |
| 10 | 145.0377 |
Things to watch for
- Tire and gauge readings are usually gauge pressure (above the surrounding air). Absolute pressure adds about 1 atm (14.7 psi).
Precision and sources
Results are calculated from the definitions above and rounded to 12 significant digits; the converter shows up to eight decimal places and the tables four. Reference: NIST Special Publication 811, Guide for the Use of the International System of Units, Appendix B.
Frequently asked questions
How many psi is one bar?
About 14.5038 psi.
Is a torr the same as a millimeter of mercury?
They are nearly identical: 1 Torr is 1/760 atm (≈ 133.3224 Pa) and 1 mmHg is 133.322387415 Pa. The difference is below one part in a million.