Bar vs PSI
Side-by-side comparison, when-to-use-each guide, and instant conversion. Reviewed for 2026.
European car manuals (universal), industrial pressure systems in metric countries, scuba diving worldwide.
US car manuals, US plumbing and industrial systems, UK car tyres (signs at petrol stations), refrigeration in US.
| Aspect | Bar | PSI |
|---|---|---|
| Definition | 100,000 pascals (≈ 1 atmosphere) | Pounds per square inch |
| Car tyre typical | 2.2 - 2.5 bar | 32 - 36 psi |
| 1 atmosphere | 1.013 bar | 14.7 psi |
| Scuba diving | 20-30 bar (cylinder) | 2,900-4,400 psi |
Frequently asked
What's 35 psi in bar?
35 psi = 2.41 bar. Most modern petrol stations in the UK have gauges marked in both, so this matters less than it used to.
Is bar an SI unit?
No — the SI pressure unit is the pascal (Pa). 1 bar = 100,000 Pa. Bar is widely tolerated alongside SI because the numbers are more practical for engineering.
Frequently asked questions
What's 35 psi in bar?
35 psi = 2.41 bar. Most modern petrol stations in the UK have gauges marked in both, so this matters less than it used to.
Is bar an SI unit?
No — the SI pressure unit is the pascal (Pa). 1 bar = 100,000 Pa. Bar is widely tolerated alongside SI because the numbers are more practical for engineering.