The Beer Dissolved CO2 & Degassing Calculator tells you how much carbon dioxide is dissolved in beer at equilibrium for a given temperature and head pressure. That lets you set the right regulator pressure for force carbonation — or plan a controlled degas in a closed fermenter or keg.
How it works
CO2 solubility in beer depends on temperature and the partial pressure of CO2 above the liquid. As beer gets colder, it holds more CO2 at the same pressure; as pressure rises, more gas dissolves. The tool uses the widely used empirical carbonation relationship fitted to brewing data:
volumes = (P + 14.695) × (0.01821 + 0.09011 × e^(−(T−32)/43.11)) − 0.003342where P is the gauge pressure in psi and T is the beer temperature in °F.
The P + 14.695 term converts gauge to absolute pressure. The result is in CO2
volumes, which the calculator also converts to grams per litre
(g/L ≈ volumes × 1.96).
Carbonation and degassing
To carbonate, pick the target volumes for your style and read off the pressure to hold at your serving temperature. To degas a closed vessel, lower the head pressure or warm the beer — both reduce the equilibrium dissolved CO2, driving gas out of solution. Comparing two scenarios in the tool shows exactly how much CO2 you will release.
Worked example
At 4°C (39°F) and 12 psi, beer carbonates to roughly 2.4 volumes — a typical lager level. Drop the pressure to 0 psi and the equilibrium dissolved CO2 falls sharply, which is how spunding and pressure release work. Equilibrium takes time to reach: forced carbonation at a set pressure can take days at rest, faster if you agitate.
Target carbonation by style
Different beer styles are served at different carbonation levels, and getting this right affects perceived mouthfeel, aroma release, and overall character. Below are typical target ranges — the calculator helps you find the serving pressure to achieve each.
| Style | Typical CO2 volumes |
|---|---|
| British cask ale | 1.0 – 1.5 |
| Irish stout (served on draught) | 1.2 – 1.5 |
| American lager | 2.5 – 2.8 |
| German Hefeweizen | 3.5 – 4.5 |
| Belgian witbier | 2.8 – 3.3 |
| India Pale Ale | 2.2 – 2.7 |
| American wheat / Berliner Weisse | 3.0 – 4.0 |
Craft styles vary; always check the specific recipe or style guidelines if precise carbonation is important.
Force carbonation versus natural conditioning
Force carbonation in a closed keg is faster and more controllable. You set the regulator to the target pressure for your serving temperature, wait for equilibrium (usually 1–3 days at rest, or a few hours with agitation by rolling or gas-purging), then adjust the serving pressure to maintain the dissolved level while dispensing.
Natural conditioning in sealed bottles or a pressure fermenter relies on residual or added sugar to produce CO2 in situ. The final carbonation depends on the quantity of fermentable sugar added and the fermentation temperature. Because there is no way to bleed off excess CO2 easily in a bottle, accuracy matters more — undershoot and you get flat beer, overshoot and you risk over-carbonation. The calculator’s ability to show CO2 volumes at any pressure is helpful for estimating where a naturally conditioned batch has ended up if you know the temperature it conditioned at.
Spunding: capturing fermentation CO2
Spunding is the technique of sealing the fermenter toward the end of fermentation to capture the last CO2 the yeast produces and use it to carbonate the beer. A spunding valve holds back pressure to a set PSI, and when fermentation finishes, the dissolved CO2 at that pressure and temperature becomes the final carbonation. The calculator lets you predict that carbonation level in advance: set the pressure you plan to spund at and the expected end-of-fermentation temperature, and read off the resulting CO2 volumes. Compare that to your target for the style before committing to the spunding pressure.