I normally wear a size 8.5 to 9, depending on the shoe. I ordered a 9 M hoping that it would fit since some of the reviews said these shoes run small. They fit great! I have some vacant space in the toes but I have short toes so I was expecting something like that. I don't think it will cause any issues. I had no problem getting them on and putting my toes in their slots.  And they are super comfy and light. I was very surprised at how lightweight they are. I'm excited to take them out for my first trek.