The pascal (Pa) is the SI base unit of pressure, defined as one newton per square meter, used in physics, engineering, and material science. While it is the scientific standard, everyday pressures are more commonly expressed in kilopascals or megapascals because one pascal represents an extremely small pressure. One pascal equals 0.00001 bar or about 0.000145 psi.

The bar is a metric pressure unit equal to 100,000 pascals, widely used in meteorology, oceanography, and industrial applications because it closely approximates atmospheric pressure at sea level. Tire pressure gauges in Europe, scuba diving depth ratings, and weather maps all commonly reference bars or millibars. One bar equals approximately 0.9869 atmospheres or 14.504 psi.