Atmospheric pressure

Atmospheric pressure is the amount of force exerted over a surface area, caused by the weight of air molecules above it.

As elevation increases, fewer air molecules are present. Therefore, atmospheric pressure always decreases with increasing height. A column of air, 1 square inch in cross section, measured from sea level to the top of the atmosphere would weigh approximately 14.7 lb/in2. The standard value for atmospheric pressure at sea level is:

29.92 inches or 760 mm of mercury

1013.25 millibars (mb) or 101,325 pascals (pa).

See aslo: atmosphere, standard pressure