I forcecarb every batch over 2 gallons. I do this primarily because I have no way of measuring the amount of CO2 already present when I calculate my priming sugar. Is there a way to estimate disolved carbon dioxide in a beer before packaging?

I heard jamil z. come up with some crazy balloon idea on brew strong, I'm hoping for an answer that doesn't use the word "eyeball":)

2 Answers 2


I think the best way is to use a carbonation table similar to the one on the attached ein conjunction with devices that measure pressure and temperature. In the past I have used a destructive method with a tool that fitted a crowned bottle of finished beer. The procedure was simple 1. attach to the top of the bottle 2. pierce the bottle and push down the dial temp indicator. 3. Agitate the bottle till room temperature is achieved. 3. Read of pressure and temperature = CO2 vols on chart http://www.kegerators.com/carbonation-table.php I will look to see if I can locate the device I used in the past, they were simple and robust. Alternatively if you all ready have a pressure guage on your keg, you know the beer is stable and you know the temperature. You could do it with out the bottle test and loss of a product. Although I think the agitation and temperature normalization is probably necessary for accuracy. The method I describe was used and may still be used as a bottling line CO2 check in a commercial brewery. Hope this helps

  • Can I do this on my very lowly carbonated beer in the primary? I'm trying to define how much sugar is necessary given the residual CO2 from fermentation.
    – dana
    Commented Dec 21, 2011 at 12:49
  • Yes I think you can but I am not sure till tested, if very low is at a point where you are coming close to racking from primary to secondary there may be as much as 1 vol of CO2 in the beer already. I have had a look at equipment there is a wide variety of kit available. The design I used has been complicated by adding digital stuff etc. but there is some more basic equipment on the trading web sites. I would suggest that if it is very low CO2 say barely perceptible on the toung ( circa <= 1vol) best to a ultasonic bath to agitate a sample of beer, ensure it is at room temp or higher
    – Delboy
    Commented Dec 21, 2011 at 13:17
  • I understand your answer in theory, but what sort of pressure device are you recommending? Is there a pressure device I can attach to my carboy?
    – dana
    Commented Dec 21, 2011 at 23:11
  • A sealable container, hygienic pressure guage and dial thermometer. This can be used for measuring CO2 at all stages of the process (except mashing & boiling:-)) Here is a link to an example of a field instrument for measuring CO2 by sampling ignore the cost it is only and example of a design. It should be simple enough to build your own. chicompany.net/… alternatively follow the calculator link provided by mdma in his answer below.
    – Delboy
    Commented Dec 22, 2011 at 12:39

The priming calculator on tastybrew computes residual CO2 based on the highest temperature that the wort reached during fermentation. By definition, the beer has 1 vol CO2 at this point (the beer is saturated with CO2 at that temperature and pressure.)

When the beer is chilled for serving, the volume of residual CO2 decreases, meaning there is less than one volume of residual CO2 in the served beer.

Skotrat has a nice article that lists volumes of residual CO2 based on fermentation temperature although it's not clear what the reference serving temperature is. Since 60F has 1 vol in the table, then I assume 60F is the serving temperature.

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