Beer Carbonation Calculator

Priming sugar for a target CO2 volume with corn sugar, table sugar, or DME.

What it does

Bottle conditioning adds a small amount of fermentable sugar to finished beer, then seals the beer so the yeast produces CO2 in the bottle. The goal is a specific carbonation level, measured in volumes of CO2. One volume means one liter of CO2 at standard conditions dissolved in one liter of beer. A typical ale is carbonated to about 2.4 volumes, while a German wheat beer may be closer to 3.0.

The beer already holds CO2 from primary fermentation. The amount depends on the highest temperature the beer reached after fermentation, because gas solubility falls as temperature rises. A beer held at 68 degrees Fahrenheit often carries about 0.8 to 0.9 volumes. A beer that was cold crashed may hold more. The priming sugar only has to make up the difference between the target and the residual, not the whole target.

The calculation converts the CO2 gap into grams of CO2, then into grams of sugar. The Brewers Association uses 0.46 grams of CO2 per gram of fermentable extract and 1.976 grams of CO2 per liter per volume. Corn sugar is about 91 percent solids, table sugar is essentially 100 percent, and dry malt extract is about 75 percent fermentable. That is why the same target needs different weights of each sugar.

The default is 5 gallons of beer at a target of 2.5 volumes with 0.9 volumes already present, primed with corn sugar. The gap is 1.6 volumes, which needs 59.8 grams of CO2 and 143.0 grams of corn sugar, or 5.04 ounces. The sugar rate is 7.55 grams per liter. The metric default uses 18.93 liters and returns the same numbers.

The result is only as good as the residual CO2 estimate. A beer that is not fully attenuated can keep fermenting in the bottle and produce far more CO2 than planned. A beer with an active contaminant can do the same. Check the final gravity over two or three days, keep the priming sugar evenly mixed, and use bottles rated for the pressure. Over-carbonated bottles can gush, crack, or explode.

How to use

1. Choose imperial or metric. Use the volume that actually goes into the bottling bucket.
2. Enter the target carbonation for the style. Ales are usually 2.2 to 2.6 volumes; lagers and wheat beers are higher.
3. Enter the residual CO2. If you do not know it, use about 0.9 volumes for a beer held near 68 °F.
4. Pick the priming sugar. Corn sugar is the standard; table sugar works; DME needs a larger weight.
5. Read the sugar weight and the rate per liter. Weigh the sugar on a scale rather than measuring by volume.
6. Dissolve the sugar in a cup or two of boiling water, cool it, add it to the bottling bucket, and rack the beer on top without splashing.

Formula

target volumes

Desired carbonation in volumes of CO2.

current volumes

CO2 already dissolved in the beer after fermentation.

beer volume

Volume going into the package, in liters.

1.976

Grams of CO2 per liter per volume of CO2.

0.46

Grams of CO2 produced per gram of fermentable extract.

solids

Fermentable solids fraction of the sugar: 0.91 corn, 1.00 table, 0.75 DME.

The 1.976 factor comes from the density of CO2 at standard conditions and is the convention used by the Brewers Association for package conditioning. The 0.46 factor assumes the sugar is fully fermentable and that the yeast converts it efficiently. Corn sugar is sold with a small amount of moisture, so its solids fraction is about 0.91. Table sugar is treated as 1.00. DME is a mix of fermentable and unfermentable sugars, so 0.75 is a practical estimate; the actual value depends on the extract. The formula does not add sugar for yeast rehydration, fining, or hop creep, and it does not subtract CO2 lost during transfer.

Worked example

Reference table

Limits

• Uses an estimated residual CO2. The actual value depends on fermentation temperature, pressure, and beer composition.
• Assumes the beer is fully attenuated and has no fermentable sugar left before priming.
• Sugar solids and fermentability vary by product, especially for DME.
• Does not replace a package pressure safety check. Bottle strength, fill level, and storage temperature still matter.

Common mistakes

• Using the kettle volume instead of the volume that reaches the bottling bucket.
• Ignoring residual CO2 and priming for the full target.
• Using the corn sugar weight when the recipe calls for DME, or the reverse.
• Measuring sugar by volume instead of weight.
• Bottling before the final gravity is stable for two or three days.
• Storing bottled beer in a hot place, where the pressure can exceed the bottle rating.

Try it yourself

Quick checks. Answers sit tucked under each question.

Questions

Sources

• Brewers Association: Preventing Package Over-Pressurization
• American Society of Brewing Chemists: Carbon Dioxide Solubility in Beer

Related calculators