Would there be any additional effect on calculated ABV after priming sugars have been added and carbonation has taken place, or is it too negligible to make any difference? At the momen5 I am basing my final ABV on the diff between OG and the FG prior to bottle priming and carbonation. Just curious really. Cheers, Edd

( [CO2]final - [CO2]start ) * 0.076 = ABV will give you a reasonable estimate of alcohol contribution from priming under "normal" conditions, where [CO2] is the CO2 level in grams per litre. If you work in volumes use 0.15 as the factor. You must then consider the dilution if you prime with syrup rather than sugar.

How on earth do I work out CO2 levels or is there something obvious that I am overlooking? I primed with dextrose.

There are mathematical formulae and there are online calculators that you can use to work out residual co2 levels and how much priming sugar is required to get desired co2.

There's fermentation occurring, so yes the ABV is increased. I used to add another 0.3-0.4 to the calculation.

Edd - I’m not a pro here and I can’t speak for the accuracy - a contributor here to the forum a while back said the site linked below was a bit of a gift back to the forum for advice he’d had over the years. http://www.thebrewlist.com/calculator/sugar-priming It may help with calculations. As for beer styles and Co2 volumes check this out: https://www.brewersfriend.com/keg-carbonation-calculator/ That said a google search for ‘beer Co2 volume’ will give you plenty to read on the topic. You can work by feel after a fair bit of practice but always good to read widely and get your feels over a brew or 10. Not sure if this has helped but it’s helped me.

Multiply the glucose* you added by 0.9 it will give you the added [CO2]. To cut to the chase, [glucose added in g/l] x 0.07 = change in ABV. Again this is net of any dilution from the use of syrup but you didn't say you used syrup. * dextrose is just a silly name home brewers use when they mean glucose.