I don't know how many carbs are in xylitol (or if it's carb-free?) so I can't answer your specific question. But what I can tell you is that regular powdered splenda has carbs because of the filler in it - maltodextrin. So obviously if you have another option that doesn't have those fillers/carbs, keep using that and just subtract what carbs were calculated for powdered splenda (just as I would because I use the liquid syrups only now).