The SI unit for pressure is which of the following?

• A. Pa
• B. kPa
• C. psi
• D. Bar

Answer: (B)

Pressure is defined as force per unit area, with the SI unit being the pascal (Pa), which equals one newton per square meter. A kilopascal (kPa) is simply 1000 pascals, so it is also an SI unit but a larger, convenient scale for many measurements. For example, typical atmospheric pressure is about 101.3 kPa, and tire pressures are often expressed in the hundreds of kPa.

Psi (pounds per square inch) is not an SI unit—it's an imperial unit. Bar is a metric unit used widely but not part of the SI; 1 bar equals 100,000 Pa but is not the SI base unit. So, in strict terms, the SI base unit for pressure is the pascal, while the kilopascal is a commonly used SI-derived unit for practicality.