I wear a size 5 and can usually fit in a size 36 cycling shoe. I don't spin so I don't know much about the 'spin' cycling shoes but I have a pair of Specialized road shoes and Shimano MTB shoes both in a 36 that fit great. And amazingly if you look around they aren't too hard to find. On the other hand with 'normal' shoes I often can't find anything smaller than a 6.