I have what I think is an rather average 7.5" (190mm) wrist. I think it would be helpful to have watch drops with a photo or two of the watch on the wrist (preferably on two different wrist sizes). Some watches wear larger/smaller for a variety of reasons. This is especially needed when you get into 44mm and larger cases.
phx_shmGoogling around (some answers reflect the fact that while there's a difference between median and average, many don't understand that) it appears you are correct with 180mm (7.1") the most common answer.
Thumper58I was just about to say, what good's an average when the median could be totally different.
Though, the average person often means median when they say average anyway... ;)