Barometric pressure is just the same as atmospheric pressure. It is called barometric pressure because the instrument used to measure is called barometer. It is the pressure exerted by the air at a certain altitude. Since it is the pressure exerted by the air, it is also known as the weight of the air above the Earth. Depending on the altitude at which the measurement is done, barometric or atmospheric pressure varies, but the barometric pressure at sea level is 1 atm (atmosphere). It is equivalent to 101325 Pa (Pascal), 760 torr, 760 mm Hg and 1.01325 bar.