Forehead width
The distance across the widest part of the forehead, usually about halfway between the brows and the hairline.
Forehead width is measured across the brow from one side of the hairline to the other at its widest point. It is the measurement that marks out a heart-shaped face, where it is the widest of the three widths, and a triangle face, where it is the narrowest. Opticians compare it with the frame front: a frame a little wider than the temples usually sits comfortably and looks in proportion.