One Atmospheric Pressure
q The average air pressure at sea
level is equivalent to the
pressure produced by a column
of water about 10 meters (or
about 76 cm of mercury
column).
q This standard atmosphere
pressure is often expressed as
1013 mb (millibars), which
means a pressure of  about 1
kilogram per square centimeter
(14.7lbs/in2).
(from The Blue Planet)