Atmosphere is a unit of measure equal to the average atmospheric pressure at sea level. In the metric system, an atmosphere is measured in newtons per square meter (N/m2), called a pascal (Pa). One atmosphere (atm) equals 101,325 Pa or 14.696 pounds per square inch (lbs/in2). The atmosphere has been largely replaced by the bar, defined as 100,000 Pa. Another common unit of pressure is millimeters of mercury (mm Hg at 0 °C), called a torr. One torr equals 1 mm Hg or 133.3 Pa. See also Barometer ; Boiling point ; Pascal ; Pressure .
