It partly depends how much sugar/dextrose etc you prime with. I found this link, a wine makers site, which suggests that 17g of sugar per litre will add 1% ABV. Calculating the ABV
So if you do a fairly average (or the only possible according to my LHBS :lol: ) prime with dextrose of 180g for a 23 litre batch, you are adding the equivalent of 6.8g sugar per litre, or 0.4% ABV. So all you have to do is work it out from there.
Confused, you will be, after the next episode of ...beer.