Force Carbonation Calculator (Keg PSI)
Regulator pressure to force-carbonate a keg to a target CO₂ volume at your fridge temperature — set-and-forget PSI, burst-carbonation shortcut, and the serving-line length to balance it.
How it works
psi = −16.6999 − 0.0101059·T + 0.00116512·T² + 0.173354·T·V + 4.24267·V − 0.0684226·V² (T in °F, V in volumes of CO₂)
Carbon dioxide dissolves into beer until the gas pressure above it balances the gas in solution, and colder beer holds more gas at the same pressure. The regression above fits the standard carbonation chart, giving the regulator setting that, left for a week or two, lands the keg exactly at the target volume. Burst carbonating at higher pressure gets there in a day but risks overshooting; the safest shortcut is a day at +20 psi followed by the equilibrium pressure. Once carbonated, the beer must be served through enough line resistance to bleed off that pressure, otherwise it foams — thin 3/16-inch line drops about 3 psi per foot, which is why kegerators typically run 8–12 feet of it.
Worked example
3 °C (37 °F) and 2.5 volumes: about 10.9 psi. With 3/16″ line and the tap 0.6 m above the keg the balance formula gives roughly 3 ft; in practice most systems use a little more line (5–6 ft) for a slower, foam-free pour.
Frequently asked questions
Why does my beer foam even at the right pressure?
Usually the line is too short or the beer is warmer than the fridge thermometer shows (kegs near the compressor or door). Add line length or let the keg cool longer.
Does the regulator gauge read the same in the fridge?
Yes — pressure is pressure, but the CO₂ cylinder should be at room temperature outside the fridge for a steady reading.
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This calculator is for educational purposes. Double-check important results before acting on them.