Ambient pressure

Almost any place in the universe will have an ambient pressure, from the hard vacuum of deep space to the interior of an exploding supernova.

The ambient atmospheric pressure at sea level is not constant: it varies with the weather, but averages around 100 kPa.

In fields such as meteorology and underwater diving, it is common to see ambient pressure expressed in bar or millibar.

Ambient pressure may in other circumstances be measured in pounds per square inch (psi) or in standard atmospheres (atm).

In underwater diving the industry convention is to measure ambient pressure in terms of water column.