The ideal pavilion angle of 40.75 degrees corresponds to a pavilion depth percentage of approximately 43%. Again this is important to bear in mind for understanding ideal depths and for communicating these facts to other dealers or to retail clientele. In the figure below, note the relationship of flatter and steeper angles to the corresponding depth percentages.
In addition to correct pavilion angles, consistent pavilion angles are also important to achieve proper symmetry in the finished diamond. You will often see diamonds with off-center culets. This is caused by the cutter’s choice in leaving the pavilion angles inconsistent. For example, one side is 39.5 degrees and its opposite is 42.5 degrees allowing the culet to favor the higher angled side.
An off-center culet may also be caused by inconsistent depths of the pavilion main facets. This is obvious when viewing the girdle plane, which should run parallel to the table.