Round diamonds are the only diamond shape that the GIA grades for cut. How well a diamond is cut is the single most important factor when purchasing a round diamond. The GIA assigns round diamonds with the following cut grades: excellent, very good, good, fair, and poor. We personally only recommend purchasing round diamonds with an excellent cut rating, which is the highest cut grade the GIA assigns. Though some diamond search engines may be populated with the term “ideal cut,” remember that your GIA certificate will never define cut as “ideal.”
The table below serves as a general guideline for evaluating the cut of a round diamond. GIA takes these and other factors into consideration when assigning a cut grade. We have also populated our own “ideal cut” criteria in the table below to help you pick out the best of the best round cut diamonds.