I normally wear a US size 10. However a 10 will fit like a 9.5 in this shoe, or maybe even a 9. I've returned a 10 for an 11 , which fits like a 10.25 if that size existed. My first use of the shoe was a 5 mile hike in muddy conditions with 25+ pounds. The shoes worked incredibly well. Keep in mind that these shoes have absolutely no arch support. I have used them on hikes, creek walks and kayaking. So far they've held up well. Update: I have used these shoes as water shoes when kayaking. After a year they come loose at the toes where the rubber sole connects to the fabric. Otherwise, they wisely persevered.