The pascal (symbol: Pa) is the unit of pressure in the International System of Units (SI). It is also used to quantify internal pressure, stress, Young's modulus, and ultimate tensile strength. The unit, named after Blaise Pascal, is an SI coherent derived unit defined as one newton per square metre (N/m). It is also equivalent to 10 barye (10 Ba) in the CGS system. Common multiple units of the pascal are the hectopascal (1 hPa = 100 Pa), which is equal to one millibar, and the kilopascal (1 kPa = 1,000 Pa), which is equal to one centibar.
The unit of measurement called standard atmosphere (atm) is defined as 101325 Pa.Meteorological observations typically report atmospheric pressure in hectopascals per the recommendation of the World Meteorological Organization, thus a standard atmosphere or typical sea-level air pressure is about 1,013 hPa. Reports in the United States typically use inches of mercury or millibars (hectopascals). In Canada, these reports are given in kilopascals.
