**
Atmosphere
** -
A unit of measurement defined as 101,325 Pascals. The typical pressure
at sea level varies around one standard atmosphere (atm). Atmospheric
pressure

*P*
can be calculated via the following equation:

**
Bar
** -
A unit of measurement equivalent to
1×10^{5}
Pascals.

**
Barometer
** -
A device used to measure atmospheric pressure.

Barometers.

**
mm Hg
** -
A unit of pressure commonly used with the barometer. It corresponds to 1
torr and 1/760 atm at 0
^{
o
}
Celsius only.

**
Pascal
** -
The SI unit of pressure. 1 Pascal =
1 N/m^{2}
.

**
Pounds per Square Inch
** -
A unit of pressure commonly used in the United States. 1 psi =
1 lb
in^{-2}
. 14.6960 psi corresponds to one atmosphere.

**
Pressure
** -
Pressure = Force/Area. The standard atmospheric pressure is 101,325 Pascals.

**
Torr
** -
A unit of pressure closely related to mm Hg, but more convenient and
absolute. 1 Torr = 1 mm Hg at 0
^{
o
}
Celsius. 1 Torr always equals 1/760
atm, irrespective of the temperature.