CO2 Volumes Calculator
Dissolved CO2 volumes from keg temperature and applied pressure.
Temperature in the keg
Gauge pressure on the regulator
- volumes
How it works
At equilibrium the carbonation a keg reaches is fixed by its temperature and the gauge pressure you apply. This is the complement of the keg-pressure formula: feed in temperature and PSI, get back the dissolved CO₂ in volumes.
vols = (P + 14.695)(0.01821 + 0.090115·e^(−(T−32)/43.11)) − 0.003342
T in °F, P in psig
Sources: carbonation-volumes equation as used by Brewer's Friend.
Assumes the keg has reached equilibrium at a steady pressure. If you just set the gas or recently shook the keg, the real carbonation is still catching up to this figure.
Frequently asked questions
- What does "volumes of CO₂" mean?
- One volume is one litre of dissolved CO₂ gas (at standard conditions) per litre of beer. Most beers land between 2 and 3 volumes; this tells you where your keg sits given its temperature and applied pressure.
- How is this different from the keg carbonation calculator?
- This is the inverse. The keg carbonation calculator takes a target carbonation and gives the pressure to set; this takes the pressure you are actually applying and tells you the carbonation level you will reach at equilibrium.
- Why does the same pressure give different volumes at different temperatures?
- Cold beer dissolves more CO₂ at any given pressure. Holding 12 PSI on a 4°C keg carbonates it noticeably more than 12 PSI on a 12°C keg, so always read volumes against your actual keg temperature.