PSI vs Bar
Two units of pressure that show up on every tire gauge, espresso machine and air compressor.
| PSI (pounds per square inch) | Bar | |
|---|---|---|
| Definition | ≈ 6,894.76 Pa | Exactly 100,000 Pa |
| 1 bar | = 14.5038 PSI | = 1 bar |
| Atmospheric (sea level) | ≈ 14.7 PSI | ≈ 1.013 bar |
| Used in | US, UK tire pressure | EU spec sheets, espresso |
- Familiar in US automotive
- Fine resolution for tires
- Decimal-friendly
- International standard
When to use which
Use PSI for US tires, hydraulic systems and most consumer products.
Use bar for European spec sheets, scientific work, and high-pressure systems (steam, espresso, dive gear).
Historical context
The pound-force per square inch dates to early steam engineering. The bar was coined in 1909 by Vilhelm Bjerknes for meteorology because atmospheric pressure varies around 1 bar.
Practical recommendation
Related tools
FAQs
Is 1 bar exactly 1 atmosphere?+
Close but not exactly — 1 atm = 1.01325 bar.
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