How do I work out the desired volume (CO2) when force carbonating my beer?

Different styles of beer can have various desired carbonation levels.

For example, a higher carbonation level (3.0 - 4.5 volumes of CO₂) is desirable in a Lambic or Saison, while a lower carbonation level (1.2 - 2.0 volumes of CO₂) is common in many British-style ales.

If your beer is in a keg, carbonating it to the correct level will depend on two major factors: 

• the temperature of the beer, 
• and the amount of pressure (pounds per square inch or PSI) of the CO₂ that you are applying to your keg through your gas regulator.