The pascal (symbol: Pa) is the SI derived unit of pressure, used to quantify internal pressure, stress, Young's modulus and ultimate tensile strength, defined as one newton per square metre. It is named after the French polymath Blaise Pascal, known for his contributions to hydrodynamics and hydrostatics.
Common multiple units of the pascal are the hectopascal (1 hPa ≡ 100 Pa), which is equal to 1 milibar (mbar), the kilopascal (1 kPa ≡ 1000 Pa), which is equal to 1 centibar (cbar). Other units include the megapascal (1 MPa ≡ 1,000,000 Pa), and the gigapascal (1 GPa ≡ 1,000,000,000 Pa).
The unit of measurement called standard atmosphere (atm) is defined as 101.325 Pa, and approximates to Earth's average atmospheric pressure at sea level. Meteorological reports typically state atmospheric pressure in hectopascals, as a recommendation of the World Health Organization (WHO), and a typical sea-level air pressure stands at around 1013 hPa. United States weather reports use either hectopascals (milibars) or inches of mercury, while kilopascals are generally used in Canada.