They run a little small. I would say take your general shoe size and go up 1 and you will be happy. I ended up returning and getting the taller version without the zip side as the next size in these was way pricier. Honestly the zip side seemed a little stiff and may irritate your ankle anyway. It also didn't seem that useful to leave the boots laced and tied and use the zip side. You can remove them ok with them unzipped, but putting them on you will probably have to untie the laces anyway. Would have liked this height without the zip side. They are also pretty tall for 6" boot. I went to the 8" version and they are very tall.