Proportions of the Humane Face Portraiture http://www.portraitclub.co.uk/the-proportions-of-the-face/

The basic rules of thumb for the proportions of the face are: The eyes are half way between the point of the chin and the top of the head. The width of the face is divided into fifths, of which the eyes, the gap between the eyes, and the space between the eyes and the side of the head are all 1/5. The base of the nose is half-way between the point of the chin and the brow-line. The ears are roughly from the level of the brow-line to level of the base of nose. The interstice of the mouth (the meeting of the lips) is roughly 2/3 of the way from the point of the chin to the base of the nose. The basic rules of thumb for the proportions of the face are:

The eyes are half way between the point of the chin and the top of the head.

The width of the face is divided into fifths, of which the eyes, the gap between the eyes, and the space between the eyes and the side of the head are all 1/5.

The base of the nose is half-way between the point of the chin and the brow-line. The ears are roughly from the level of the brow-line to level of the base of nose.

The interstice of the mouth (the meeting of the lips) is roughly 2/3 of the way from the point of the chin to the base of the nose.