A single pascal is a very small amount of pressure, so chemists and atmospheric scientists usually report measurements in kilopascals or megapascals instead. Standard atmospheric pressure at sea level equals exactly 101.325 kilopascals, or 101,325 pascals. In strict SI usage, the pascal has replaced older pressure units like the atmosphere and the torr, though those older units still appear often in traditional laboratory settings and older textbooks.
Using pascals consistently is important in thermodynamic calculations, since equations relating pressure, volume, and temperature require a single, standard unit system to give correct results. In base SI units, one pascal equals one kilogram per meter per second squared. This unit appears directly in the ideal gas law, PV = nRT, whenever pressure must be expressed in pascals to match the other units in the equation.
The pascal is a derived unit, meaning it is built from the more basic SI units of mass, length, and time rather than defined independently. The unit is also used outside chemistry, appearing in engineering fields to describe material stress and in meteorology to describe barometric pressure readings.