Pressure Units Guide
PSI, bar, kPa, and atm explained — with tire pressure guides for all vehicle types
Overview
Pressure is force applied per unit area. It is measured in various units depending on the application: PSI for tire pressure in the US, bar in Europe, Pascal (Pa) in scientific contexts, and atmospheres (atm) for reference.
Understanding pressure units is essential for automotive maintenance, weather forecasting, scuba diving, and many industrial applications.
Common Pressure Units
Pounds per square inch
US tire pressure
1 PSI = 6.895 kPa
Metric unit
Europe tire pressure
1 bar = 14.504 PSI
Kilopascal
Scientific, automotive
1 kPa = 0.145 PSI
Atmosphere
Sea level reference
1 atm = 14.696 PSI
Tire Pressure Guide
| Vehicle Type | PSI | bar | kPa |
|---|---|---|---|
| Passenger Car (front) | 30-35 | 2.0-2.4 | 207-241 |
| Passenger Car (rear) | 30-35 | 2.0-2.4 | 207-241 |
| SUV / Light Truck | 35-40 | 2.4-2.8 | 241-276 |
| Heavy Truck | 80-100 | 5.5-6.9 | 552-689 |
| Bicycle (road) | 80-130 | 5.5-9.0 | 552-896 |
| Bicycle (mountain) | 25-35 | 1.7-2.4 | 172-241 |
Conversion Formulas
PSI to bar
bar = PSI x 0.0689476bar to PSI
PSI = bar x 14.5038PSI to kPa
kPa = PSI x 6.89476Atmospheric Pressure
Standard atmospheric pressure at sea level:
Standard Values
- 1 atm = 101,325 Pa
- 1 atm = 1.01325 bar
- 1 atm = 14.696 PSI
- 1 atm = 760 mmHg
Weather Pressure
- High: >1020 hPa (fair weather)
- Normal: 1013 hPa
- Low: <1000 hPa (stormy)
- Hurricane: <950 hPa
Pressure in Scuba Diving
Underwater pressure increases by approximately 1 atmosphere for every 10 meters (33 feet) of depth: