In most shoes I'm a size 10.5.  I bought these in an 11 and they fit perfectly.  I was looking for a flip flop with a bit of arch support and these barely have any, but I figure some is better than none.  After years of wearing flat flip flops, I'm ready to be kinder to my feet!  These are more casual--you can't really dress up with the top strap looking so rubbery, but I still think they're really comfortable and have NO break-in time!  Great price & great shoe.