I am normally a 8.5-9. I needed the 9.5 in these even for a medium thickness sock. Once I got the right size I loved them. They are not as bulky as many of the other snow boots while still being super warm. With medium wool socks and toe warmers I wore these puppies for a week in Alaska doing many outdoor activities. Never slipped once, toes only got slightly chilly once or twice. My feet were as comfortable as my friends who were wearing much bulkier/heavier boots. Very happy with this choice.