Each facet must be cut and shaped with precision, and placed with perfect symmetry . A well cut diamond is referred to as ideal, excellent, or very good. In a well cut diamond the light enters at the top and forms a U shape and then exits back out at the top.

With a deep cut the light enters from the top and forms an L shape as it exits out the side. With a shallow cut diamond the light enters from the top and curves slightly back out at the bottom of the diamond. Too deep of cut or too shallow both interfere with the correct light reflection.