Beer carbonation calculator (volumes of CO₂)
Enter how fizzy you want the beer, in volumes of CO₂, the warmest temperature the beer reached after fermentation and the batch size. The calculator subtracts the CO₂ the beer already holds and gives the table sugar or corn sugar to add at bottling, plus the regulator pressure that holds the same carbonation in a keg at serving temperature.
Runs in your browser: nothing you enter is sent anywhere.
How to use
- Choose liters and °C or US gallons and °F.
- Enter the target carbonation in volumes of CO₂ for your style.
- Enter the warmest temperature the beer has had since fermentation ended and the amount of beer going into bottles.
- For kegs, enter the temperature the keg is kept at.
- Read the sugar to dissolve and mix in at bottling, or the regulator pressure for the keg.
How it works
CO₂ left in the beer: V₀ = 3.0378 − 0.050062 T + 0.00026555 T², with T in °F. Sugar to add: table sugar = 15.195 g × US gallons × (target − V₀); corn sugar = table sugar ÷ 0.91. Keg pressure in psi at serving temperature T and target V: P = −16.6999 − 0.0101059 T + 0.00116512 T² + 0.173354 T V + 4.24267 V − 0.0684226 V². Liters and °C are converted first; 1 psi = 0.0689 bar. These are the widely used homebrewing fits, valid for ordinary cellar-to-room temperatures.
Example
5 gallons of ale that finished at 68 °F, target 2.4 volumes:
- CO₂ left: 3.0378 − 0.050062 × 68 + 0.00026555 × 68² = 0.86 volumes;
- to add: 2.4 − 0.86 = 1.54 volumes;
- table sugar: 15.195 × 5 × 1.54 = 117 g, about 4.12 oz; corn sugar 117 ÷ 0.91 = 128 g;
- in a keg at 38 °F the same 2.4 volumes need about 10.2 psi (0.7 bar).
Tips
- Dissolve the sugar in a little boiled water, cool it and stir it gently into the whole batch, so every bottle gets the same amount.
- Use bottles rated for the pressure: above about 3 volumes ordinary thin bottles are risky.
- Bottle-conditioned beer needs about two weeks at room temperature before it is fully carbonated.
Frequently asked questions
What is a volume of CO₂?
It is the volume the dissolved gas would take up at normal pressure and 0 °C, divided by the volume of the beer. 2.5 volumes means each liter of beer holds 2.5 liters of CO₂. Many British ales sit near 1.5 to 2, lagers and American ales near 2.4 to 2.7, wheat beers and some Belgian styles above 3.
Why does the temperature after fermentation matter?
Cold beer holds more CO₂ than warm beer. Use the warmest temperature the beer reached at the end of fermentation or since: at 20 °C (68 °F) about 0.86 volumes are left, at 2 °C (35.6 °F) about 1.59. Using the bottling-day temperature of a beer that was warmer before can over-carbonate it.
Table sugar or corn sugar?
Both work. Corn sugar sold for brewing is dextrose monohydrate, which carries water, so it gives about 91 % of the CO₂ of the same weight of table sugar; the calculator adds about 10 % more for it.
How do I use the keg pressure?
Set the regulator to the pressure shown, keep the keg at the keg temperature and wait: at a steady pressure the beer reaches the target in about a week or two. The numbers are gauge pressure at the keg; long or narrow beer lines need balancing for a good pour but do not change the carbonation.