Real-World References — click to load
Pressure Units Guide
Also searched as: pressure converter online free | psi to bar converter | kpa to psi converter | tire pressure converter Optimized for US users with American units and terminology.
The Pascal (Pa) is the SI unit of pressure — one Newton per square meter. Standard atmosphere (atm) is 101,325 Pa, the average atmospheric pressure at sea level. PSI (pounds per square inch) is the most common US unit for tire pressure and industrial applications. Medical blood pressure is measured in mmHg (millimeters of mercury).
One standard atmosphere (atm) is defined as exactly 101,325 Pascals (101.325 kPa). It represents the average atmospheric pressure at sea level. At higher altitudes, atmospheric pressure decreases — at 10 km altitude (typical cruising altitude), pressure is about 26.5 kPa (26% of sea level).
Most passenger car tires should be inflated to 30–35 PSI (207–241 kPa). The correct pressure is printed on a sticker in the driver's door jamb or the owner's manual — NOT on the tire sidewall (which shows maximum pressure). Check pressure when tires are cold for accurate readings.