About

Pressure measurement standards vary significantly by industry and region. The United States predominantly uses Pounds per Square Inch (PSI) for automotive and industrial applications, while Europe and most metric-adopting nations utilize Bar or Kilopascals (kPa). For drivers, correctly converting these values is critical for tire safety and fuel efficiency. Under-inflated tires (incorrect conversion) can lead to blowouts and increased rolling resistance. In industrial settings, hydraulic systems often require precise Bar inputs, where a miscalculation from PSI could damage sensitive seals or exceed safety valves limits.

Formulas

The Bar is a metric unit of pressure, but not part of the International System of Units (SI), which uses the Pascal (Pa). One Bar is exactly equal to 100,000 Pascals.

{

Bar = PSI × 0.0689476PSI = Bar × 14.5038

For scientific precision, the standard atmosphere (atm) is defined as 101.325 kPa, which is approximately 1.01325 Bar or 14.696 PSI.

Reference Data

Application	PSI (lb/in²)	Bar	kPa	Notes
Road Bike Tire	100	6.89	689	High Pressure
Compact Car	30	2.07	207	Standard Sedan
Standard SUV	35	2.41	241	Average Load
Light Truck	50	3.45	345	Heavy Load
Commercial Truck	105	7.24	724	Semi-trucks
Atmosphere	14.7	1.013	101.3	Sea Level
Scuba Tank	3000	206.8	20684	Full Tank
Espresso Machine	130	9.0	900	Extraction

Frequently Asked Questions

The correct pressure is not printed on the tire sidewall (that is the maximum). Instead, check the sticker inside the driver's door jamb or the owner's manual. Most passenger cars require between 30 and 35 PSI (2.1 to 2.4 Bar).

The Kilopascal (kPa) is the official SI unit for pressure. Many modern digital gauges and international standards (ISO) prefer kPa because it is part of the metric system's base 10 structure, unlike PSI.

No, but they are very close. 1 Atmosphere (atm) is defined as 101,325 Pascals, while 1 Bar is defined as 100,000 Pascals. Therefore, 1 atm is approximately 1.01325 Bar.

Yes. Pressure increases with temperature. It is standard practice to measure tire pressure when "cold" (vehicle has been parked for 3 hours) to get an accurate base reading.