Keg Carbonation Calculator
The regulator pressure that holds your target carbonation at your keg's actual temperature, from the CO2 solubility physics behind the standard ASBC table.
The beer's actual temperature, not the room's.
How this was worked out
Henry coefficient = 0.01821 + 0.090115 × e^(−(38 − 32) ÷ 43.11)
psig = (2.5 + 0.003342) ÷ Henry coefficient − 14.695 = 11.22 psi
Plugging that pressure back into deLange's own volumes equation gives 2.500 volumes, which recovers the 2.5 target because the two equations are algebraic inverses of each other — a check that the arithmetic was applied correctly, not an independent confirmation of the formula itself.
| Temp (°F) | 3 vol | 2.2 vol | 2.4 vol | 2.6 vol | 2.8 vol |
|---|---|---|---|---|---|
| 34 | 14.0 | 6.2 | 8.1 | 10.1 | 12.0 |
| 36 | 15.5 | 7.1 | 9.2 | 11.3 | 13.4 |
| 38 | 16.7 | 8.1 | 10.3 | 12.4 | 14.5 |
| 40 | 17.9 | 9.1 | 11.3 | 13.5 | 15.7 |
| 42 | 19.0 | 9.9 | 12.2 | 14.4 | 16.7 |
Why temperature and pressure trade off
CO2 dissolves into beer according to Henry's law: the amount that stays in solution at equilibrium is proportional to the pressure of CO2 above the liquid, and that proportionality itself depends on temperature. Colder beer holds more gas at a given pressure, which is why a kegerator running colder needs a lower regulator setting to reach the same target than a keg sitting in a warmer cellar.
The relationship isn't simple enough to invert by hand, which is why brewers have relied on published charts for decades. The equation this calculator uses is a fitted approximation to that same underlying data, which is what makes it possible to answer for any temperature and target rather than only the handful of points a printed chart covers.
Worked example
A beer at 36°F, targeting 2.6 volumes of CO2 — a typical carbonation level for an American ale.
The regulator should read about 11.3 psi. The published ASBC reference table gives 11.3 psi for this exact point, which the formula reproduces closely.
Checking the other direction: 11.3 psi at 38°F works out to 2.51 volumes, against the table's published 2.5 — the small gap is the fitted formula's known error, not a mistake in either direction.
Common mistake
Setting the regulator from the room temperature or the temperature the keg started at, rather than the beer's temperature once it has fully equilibrated in the fridge. A keg that hasn't finished chilling all the way through will read as needing less pressure than it actually will once it's fully cold.
Keep going
- The other way to hit the same CO2 target -- priming sugar in the bottle instead of applied keg pressure -- for whichever packaging this batch is going into. Priming sugar Calculator
Frequently Asked Questions
Why does colder beer need less pressure for the same carbonation?
Because CO2 solubility rises as temperature falls — the same physics as a warm soda going flat faster than a cold one. Colder beer already holds more CO2 at a given pressure, so it takes less applied pressure to reach the same target volumes.
Should I use the keg's temperature or the room's?
The beer's actual temperature, which for a kegerator is the fridge temperature once the keg has had time to equilibrate — typically 24 hours or more for a full keg. A keg that's only partly chilled will carbonate unevenly and the calculator's number won't hold until it's fully cold.
How long does force carbonation actually take at the calculated pressure?
This calculator gives the equilibrium pressure — what the regulator should be set to once the beer is fully carbonated and holding steady, not a timeline. Reaching that equilibrium can take days at serving pressure alone, or under an hour with agitation (rocking or rolling the keg) at a higher pressure, which is a separate technique from what this tool calculates.
Why does the calculated pressure sometimes not exactly match a published chart?
The formula used here is a close fit to the same published ASBC data that carbonation charts are built from, not a re-typing of the chart itself, so it can differ by a few tenths of a psi at some points — well within what the fit's own documentation states (about 0.01 volumes root-mean-square). The reference table below shows the published numbers directly for comparison.
Does altitude change the pressure I should set?
Yes, if you're measuring gauge pressure and reading published charts that assume sea level. Atmospheric pressure drops as elevation rises, so a keg at elevation needs a higher gauge pressure reading to reach the same absolute pressure — roughly an extra 1 psi per 2,000 feet of elevation. This calculator does not include that adjustment.
Sources. The underlying data is the American Society of Brewing Chemists' CO2 solubility table (Methods of Analysis, 5th ed., 1949). Two independent publications of it were cross-checked: the Brewers Association's "Facts About Draught Beer Carbonation" reproduces the ASBC table directly and cites it by name, and A.J. deLange's "CO2 Volumes in Beer" fits a closed-form equation to the same table and states its accuracy (root-mean-square error of about 0.01 volumes). Both retrieved 22 September 2026. This calculator uses deLange's equation 2.1 so it can answer for any temperature and target; the reference table shown on this page reproduces the Brewers Association's published numbers exactly, for comparison. This tool does not adjust for elevation.
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