Im an average size 8 US but I ordered a large and it fits just perfect. If I wouldve ordered a medium I believe it wouldve been tight in all the wrong places Im 5 foot four and the jacket comes right to my knees. Fits nicely  in the hood and the hood pulls up nicely without falling over my face. I commute every morning so this will be my fall jacket. Glad I could find one for a reasonable price.