On August 1st, 2005, GIA announced that it will add a Cut grade to its round brilliant diamond grading reports starting January 1, 2006. According to GIA, there is no single set of proportions that define a well-cut round brilliant diamond. You can estimate your diamond’s Cut grade using the free GIA Facetware™ Cut Estimator online tool at http://www.diamondcut.gia.edu/.

AGS Laboratories also issues diamond Cut grade on its Diamond Quality Document. The right is AGS's ideal cut proportions for a round brilliant diamond.

Diamond Cut grade has always been a controversial topic. It will be interesting to see how a GIA Excellent Cut grade compares to AGS Ideal Cut grade.