I am 5'7 180 lbs and i got the large. I tried on the medium, and the length was good but it was way tight around the chest/arms. The large length is maybe 2 or 3 inches above my knee. If you are tall and skinny, I'd say large.
Looks real good, the worst thing about it is the coat kinda absorbs oil, or anything. I bought the burgundy colored coat and the more I wear it the more it gets dark around the cuffs. Not a big problem, but the color of the coat shows off dirt easily. Also, this coat isn't much of a full season coat. I don't feel like this coat could hold up against a full day of riding while its snowing.