A brilliant round cut diamond isn’t just one of the best diamond shapes – it’s the diamond shape. Created in 1919 by engineer and diamond cutter Marcel Tolkowsky, the brilliant round utilizes an ideal ratio to maximize its “fire” and brilliance. Unlike the old mine cut and other earlier ancestors, the round doesn’t focus on carat size. In fact, up to half of the rough diamond is wasted in a round cut.

Browse our engagement rings with the brilliant round diamond cuts

Tolkowsky’s Proportions

A brilliant round cut diamond has 58 facets in an octahedron shape. Unlike other forms, the round isn’t cut too shallow or too deep, which prevents light from leaking out the bottom or the side. Instead, a brilliant round cut diamond shines out the top. While Tolkowsky wasn’t the first to suggest these new proportions, he gave the style its mathematical foundation. Diamond cutters had already begun to use techniques that emphasized light distribution at the cost of carat weight, thanks to large diamond deposits discovered in the nineteenth century.

Marcel Tolkowsky invented the ideal diamond cut.

Modern Popularity

The round is easily the most popular diamond shape.  It’s often used for engagement rings, though many earrings also feature brilliant round cut diamonds. Since it emphasizes brilliance over clarity, the round cut can help augment lesser stones with blemishes better than fancy cut alternatives.