i think the (average) is either 2 1/4" or 2 1/2"...that seems to be the Preferance. I personally on most quilts prefer a narrower binding but if i'm binding one that is quite heavy/thick/lofty---like flannel or wool quilts---i do use a 2 1/2"..it is a personal choice- as long as you can A) fold it in half; B) stitch it to one side; C) fold it over & stitch it to the other side- covering the stitching from the first side--- it is an ok width---some people even like them much wider- so they are almost like an extra border/design element- use what you like & works for you---your binding should be *Full* though---meaning the batting & fabric inside the fold should fill the space.