The most popular and quite simply the best diamond preferred in diamond rings, as well as the most "brilliant" diamond cut is the Round Brilliant (Cut) diamond. Other names used to describe this cut are: Old European Cut, American Ideal Cut, American Standard Cut, Brilliant Cut and Modern Brilliant Cut.

Round cut is a modified form of the traditional emerald cut in a brilliant rather than step cut style which creates a bright and scintillating look. The Round Cut is really designed to provide maximum optics for the scintillation (rapid changes in the brightness of a celestial body) that gives the diamond ring that radiant sparkle, thereby placing well-cut diamonds higher on the Diamond Quality Pyramid.

A little bit about the history of round diamonds: more than a hundred years ago, a Russian Mathematician named Marcel Tolkowsky, who was a member of a large and powerful diamond family, calculated the cuts necessary to create the ideal diamond shape. In his thesis paper Diamond Design, Tolkowsky gave clear specifications in order to maximize the brilliance and scintillation of diamonds, which later became known as the brilliant cut. The suggested cut height for a Round shape is 59.3% of the diameter of the diamond, which breaks down to about 43% for the pavilion, and 16% for the height of the crown. This 59.3% is probably the most crucial dimension of the stone.

The Round Brilliant diamond consists of 57 facets and 58 with a culet. This particular cut displays the most fire and scintillation of all other cuts. No wonder that the vast majority of diamonds sold are round cut. Round shaped diamond rings are traditional choice for all occasions and preferred by many educated customers.