Understanding PSI vs BAR: Tire Pressure Units Explained
A comprehensive guide to tire pressure measurement units and how to convert between them.
What Are PSI and BAR?
PSI
Pounds per Square Inch
PSI is the imperial unit of pressure measurement commonly used in the United States. It measures the force applied over one square inch of area.
BAR
Metric Atmospheric Pressure
BAR is the metric unit used in most countries worldwide. One BAR equals approximately the atmospheric pressure at sea level.
Quick Conversion Reference
1 BAR = 14.5038 PSI
1 PSI = 0.0689476 BAR
Common Tire Pressure Conversions
| PSI | BAR | Common Use |
|---|---|---|
| 26 PSI | 1.8 BAR | Small cars, eco tires |
| 28 PSI | 1.9 BAR | Compact cars |
| 30 PSI | 2.1 BAR | Mid-size sedans |
| 32 PSI | 2.2 BAR | Most common pressure |
| 35 PSI | 2.4 BAR | SUVs, larger vehicles |
| 36 PSI | 2.5 BAR | Light trucks |
| 40 PSI | 2.8 BAR | Heavy trucks, loaded vehicles |
Which Unit Should You Use?
Always Use Your Vehicle's Recommended Unit
Check your vehicle's door jamb sticker or owner's manual. Most will display both PSI and BAR, but use whichever unit is more prominent or matches your tire pressure gauge.
🇺🇸 PSI Used In:
- • United States
- • Some parts of Canada
- • UK (alongside BAR)
- • American-made vehicles worldwide
🌍 BAR Used In:
- • European Union countries
- • Asia Pacific regions
- • South America
- • Most of the world
How to Convert PSI to BAR
Formula: PSI to BAR
BAR = PSI × 0.0689476
Example:
32 PSI × 0.0689476 = 2.21 BAR
Formula: BAR to PSI
PSI = BAR ÷ 0.0689476
Example:
2.2 BAR ÷ 0.0689476 = 31.9 PSI
Understanding Tire Pressure Gauges
Most modern tire pressure gauges display both PSI and BAR readings:
Digital Gauges
Usually have a button to toggle between PSI and BAR. Some display both simultaneously.
Analog (Dial) Gauges
Often show two scales on the same dial - PSI on the outer ring and BAR on the inner ring.
Stick Gauges
May only show one unit. Make sure it matches your vehicle's specification unit.
Common Mistakes to Avoid
❌ Mixing Up Units
Setting your tire to 2.2 PSI instead of 2.2 BAR will result in dangerously under-inflated tires. Always double-check the unit!
❌ Using Maximum Pressure from Tire Sidewall
The pressure on your tire sidewall is the MAXIMUM, not the recommended pressure. Use your vehicle manufacturer's specification.
❌ Incorrect Conversion Rounding
Be precise with conversions. 2.2 BAR is 31.9 PSI, not 32 PSI. Small differences matter for optimal performance.
Other Pressure Units
While PSI and BAR are the most common, you may occasionally encounter:
| Unit | Full Name | Equivalent |
|---|---|---|
| kPa | Kilopascal | 1 BAR = 100 kPa |
| kg/cm² | Kilogram per Square Centimeter | 1 kg/cm² ≈ 0.98 BAR |
| atm | Atmosphere | 1 atm ≈ 1.01 BAR |
Key Takeaways
- ✓PSI (imperial) and BAR (metric) are both valid tire pressure units
- ✓Always use the unit specified by your vehicle manufacturer
- ✓1 BAR equals approximately 14.5 PSI
- ✓Most modern gauges display both units for convenience
- ✓Never confuse PSI with BAR when inflating your tires