My actual foot size is between a 10.5 and 11. I've always worn size 11 shoes in a narrow width.  Thankfully, I followed the advice of people who have purchased these slippers and ordered one size larger than my normal shoe size. As I mentioned, I have a narrow width foot and these were surprisingly snug. In the beginning, these slippers were a little too snug, but it hasn't taken long to adjust or perhaps they have stretched ever so little. I think any man with a large foot would be advised to go even larger in size than I did. I know my two brothers have stout feet and I don't think they would have fit these slippers in my size. Their feet are not any longer than mine, but their width and overal foot size is substantially bigger than mine.  So I urge caution on selecting the size.  I am very pleased with my slippers, but some of those who came before me are not so pleased with the sizing issue.