I typically wear a  6 1/2 or 7 and these boots were a really small 7and fit more like a smaller 6.  I have a 15 inch calf and could not get them zipped up. (As I recall they are advertised to fit a 15 inch calf)  So I sent them back ordering a size 8.  As expected, they were a little large in the foot but no larger in the calf.  In addition the back zipper is almost impossible to pull up without the assistance of a mule team.  It is very difficult to get a grip on the zipper pull in addition to the fact that the zipper is not heavy duty to begin with.  If you have very slender legs these are the boots for you....order a size up.