"It is important in figure drawing to draw the human figure in proportion. Though there are sutbtle differences between individuals, human proportions fit within a fairly standard range, though artists have historically tried to create idealised standards. In figure drawing, the basic unit of measurement is the 'head', which is the distance from the top of the head to the chin. This unit of measurement is reasonably standard, and has long been used by artists to establish the proportions of the human figure. The proportions used in figure drawing are: An average person, is generally 7-and-a-half heads tall (including the head)." http://en.wikipedia.org/wiki/Body_proportions#Basics_of_human_proportions