Pressure is force per unit area. Different industries use different units: Pascals in science, bar in Europe, PSI in the US, and atmospheres in chemistry.
What Is Pressure?
Pressure = Force ÷ Area. The Pascal (Pa = 1 N/m²) is the SI unit. One Pascal is very small, so kPa and MPa are more common in engineering.
Standard Atmosphere
1 atm = 101,325 Pa = 101.325 kPa = 1.01325 bar = 14.696 PSI. This is the average atmospheric pressure at sea level.
Bar and PSI
1 bar = 100,000 Pa ≈ 0.987 atm. PSI (pounds per square inch) is the US standard. Car tire pressure is typically 30–35 PSI (2.0–2.4 bar). 1 PSI = 6.895 kPa.
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Frequently Asked Questions
What is the difference between PSI and bar?
PSI is imperial; bar is metric. 1 bar = 14.504 PSI. US tires use 30–35 PSI; European tires use 2.0–2.4 bar.
How do I convert kPa to PSI?
Divide kPa by 6.895. For example, 200 kPa ÷ 6.895 = 29.0 PSI.