From my experience, I always purchase my wading boots one size larger than my normal shoe size which leaves me plenty of room for the stocking foots waders I use plus an extra pair of socks for winter fishing. If at all possible, I would recommend that you go to a vendor that sells wading boots and try on their boots before buying. Most good vendors will have a "bootie" sock you can slip on before trying on wading boots to make sure that they are not too tight and that the fit is good. For me, I wear a size 8 shoe and purchase my wading boots in a size 9 and everything works great.