Post-carb ABV?

I was wondering if there is a way to find ABV after carbonation. I know the calculation for finding it post-fermentation, but I want to know my alcohol content after the priming sugar is converted. I would imagine the carb would throw off any gravity readings, so how is this accomplished? For example, in my primary right now is a hefeweizen with an OG of 1.040. I plan to bottle at 1.010 and prime with sucrose. The ABV before priming should be around 3.9-4.0%. How can I determine the additional alcohol produced from the sucrose? Or is it a negligible amount?

Pull a sample and let it sit until the CO2 is gone. Then you can get an accurate FG reading.

I just added 5oz of corn sugar to one of my recipes in Ibrewmaster and it bumped the alcohol up .2 points

Take a sample pre-adding priming sugar, then take one POST adding primary sugar, and calculate the difference. Assuming all priming sugar is eaten by the yeast, giving you carb, you should have your difference.

It is basically negligible. I can't even remember its 4 oz for priming? Equals 112 grams / 342 g/ mol of sucrose= about 0.3 mols x 46 g/ mol= ~15 grams/ ~19 liters= less than 0.01% by weight and even less for alcohol by volume as the density of ethanol is less than that of water. Not precise math but you can see its negligible.


Hope that helps!