Converting Bars to Atmospheres

This example problem demonstrates how to convert the pressure units bar (bar) to atmospheres (atm). Atmosphere originally was a unit related to the air pressure at sea level. It was later defined as 1.01325 x 10⁵ pascals. The bar is a pressure unit defined as 100 kilopascals. This makes one atmosphere nearly equal to one bar, specifically: 1 atm = 1.01325 bar.

Problem:

The air pressure outside a cruising jet liner is approximately 0.23 bar. What is this pressure in atmospheres?

Solution:

1 atm = 1.01325 bar

Set up the conversion so the desired unit will be cancelled out. In this case, we want atm to be the remaining unit.

pressure in atm = (pressure in bar) x (1 atm/1.01325 bar)
pressure in atm = (0.23/1.01325) atm
pressure in atm = 0.227 atm

Answer:

The air pressure at cruising altitude is 0.227 atm.