Unit of the air pressure is the Pascal.
As the air pressure on sea level is, on average, 101325 Pa, thus approx. 100000 Pa, it is given mostly by the number about 1000 in hectopascal (1013.25 hPa) or by the same numerical value millibar (mbar). The air pressure is mostly measured through a barometer, where often obsolete units are used. Here is: 1 hPa = 1 mar = 0.75 Torr (= mm Hg or millimeter mercury column).