That's the ONE thing that matters to me. The shoes fit well and are quite comfortable. I usually wear US size 13 sneakers so I bought a size 13. The only thing I worried about was blisters on my heel when walking on water. After spending a week at the lake with my dog, I took these shoes into the water 3 or more times a day throughout the week. Not a single blister by the end of the week. Super happy with it. I will buy them again when they reach the end of their lifespan.