<P> Atmospheric pressure , sometimes also called barometric pressure , is the pressure within the atmosphere of Earth ( or that of another planet ) . In most circumstances atmospheric pressure is closely approximated by the hydrostatic pressure caused by the weight of air above the measurement point . As elevation increases , there is less overlying atmospheric mass , so that atmospheric pressure decreases with increasing elevation . Pressure measures force per unit area , with SI units of Pascals ( 1 pascal = 1 newton per square metre , 1 N / m ) . On average , a column of air with a cross-sectional area of 1 square centimetre ( cm ) , measured from mean ( average ) sea level to the top of Earth 's atmosphere , has a mass of about 1.03 kilogram and exerts a force or `` weight '' of about 10.1 newtons or 2.37 lb , resulting in a pressure at sea level of about 10.1 N / cm or 101 kN / m ( 101 kilopascals , kPa ) . A column of air with a cross-sectional area of 1 in ( 6.45 cm ) would have a mass of about 6.65 kg and a weight of about 65.4 N or 14.7 lb , resulting in a pressure of 10.1 N / cm or 14.7 lb / in . In the United States , atmospheric pressure near sea level is commonly rounded to 15 lb / in , and expressed as `` 15 psi '' ( 15 pounds per square inch . ) </P>
<P> Atmospheric pressure , sometimes also called barometric pressure , is the pressure within the atmosphere of Earth ( or that of another planet ) . In most circumstances atmospheric pressure is closely approximated by the hydrostatic pressure caused by the weight of air above the measurement point . As elevation increases , there is less overlying atmospheric mass , so that atmospheric pressure decreases with increasing elevation . Pressure measures force per unit area , with SI units of Pascals ( 1 pascal = 1 newton per square metre , 1 N / m ) . On average , a column of air with a cross-sectional area of 1 square centimetre ( cm ) , measured from mean ( average ) sea level to the top of Earth 's atmosphere , has a mass of about 1.03 kilogram and exerts a force or `` weight '' of about 10.1 newtons or 2.37 lb , resulting in a pressure at sea level of about 10.1 N / cm or 101 kN / m ( 101 kilopascals , kPa ) . A column of air with a cross-sectional area of 1 in ( 6.45 cm ) would have a mass of about 6.65 kg and a weight of about 65.4 N or 14.7 lb , resulting in a pressure of 10.1 N / cm or 14.7 lb / in . In the United States , atmospheric pressure near sea level is commonly rounded to 15 lb / in , and expressed as `` 15 psi '' ( 15 pounds per square inch . ) </P>
atmospheric pressure at sea level in si units
atmospheric pressure at sea level in si units
about 10.1 N / cm or 101 kN / m ( 101 kilopascals , kPa )
about 10.1 N / cm or 101 kN / m ( 101 kilopascals , kPa )