I have sold a lot of shoes to a lot of guys over the course of my time not only owning my own brand but also selling shoes at Nordstrom. And in that time, one of the things that baffled me most was guys coming to try dress shoes with thick athletic socks and insisting that it would be fine. Even after telling them that doing so would result in a half size difference in fit, they continued to insist that it would be fine. And although slightly annoying, more so funny it was when they came with shoes that they felt too big after trying them with proper socks and wanted to exchange them for at least a half size down. And I always felt ‘should this not be common sense?’ The difference in a thin wool sock to a thin cotton one can be the difference between a slightly loose shoe to a well-fitting one. Socks matter, and the thicker they are, the less accurate fit you will get for trying on a brand new shoe.
Now of course, this is not to take into account people that like to wear heavy socks with their dress shoes. That of course, is a preference and perfectly fine if that is ‘how you wear your dress shoes,’ but this is more about the sense to know that when you typically wear dress shoes with thin socks, and then come to the store with athletic socks trying to find a pair of well-fitting shoes, that you are better off doing so barefoot than with your thick athletic socks.
So people. Do try to buy well fitting shoes on a whim. Go prepared. Or at least, do barefoot. But NEVER wear athletic socks to try on dress shoes if you intend to wear them with thin dress socks in the future. Or buy half size down as inevitably that will be the size you need!