atm

An atm (or atmosphere) is a unit of pressure conceived to represent Earth atmospheric pressure. It has been standardized as an exact value, a selected long-term average at sea level at the latitude of Paris, France. Equivalences:

• 101325 pascals
• 1013.25 millibars
• 1.01325 bar
• ≈14.7 pounds-force per square inch.

Other units of pressure:

• a pascal (Pa), an SI-derived unit consisting of 1 kg·m^-1·s^-2.
• a bar, 10,000 pascals, convenient for (also) being roughly Earth atmospheric pressure.
• a millibar (mbar, 1/1000 of a bar).
• a megabar (Mbar, a million bars).