A Brief History of the Round Brilliant Cut

| 3 min read

The fine art of gemstone cutting - known as lapidary - is a constantly evolving science that strives to find exciting new ways to present gemstones at their very best. But, for a century now, many would agree that the ideal classic cut for a gemstones, and especially for Diamonds, is the Round Brilliant Cut. Here, we take a brief look at how it came to be, and why it works so well.


Marcel Tolkowsky (1899-1991) is famed for inventing the Round Brilliant Cut. Both his grandfather and his father were Diamond cutters and as part of his PhD thesis, Tolkowsky published a specification sheet of what he felt were the ideal angles of facets on a round cut Diamond. This later became known as the American Ideal Cut and also the Tolkowsky Cut.

In 1919 he published a book simply called ‘Diamond Design’. He explained that if you cut a Diamond too deep or too shallow, that light would escape through the bottom and the sides of the gem. He also detailed what he believed was the perfect size of the table facet, the depth of the crown and the depth of the pavilion.

When you look at the diagram below, some of the numbers may not make sense at first, so we'll try and explain these in plain English. When you study a gem, try and view the crown (the proportion above the girdle) as a lens or looking glass (looking into the gem) and the pavilion (the portion below the girdle) as a hall of mirrors. Keeping this in mind, hopefully some of the following numbers start to make sense.

Round Brilliant Cut Dimensions

Height of the Diamond: 59.3% is the total depth percentage when compared to the diameter of the girdle. The girdle is the widest point of the gemstone.

Crown Height: The 16.2% percentage is of the diameter of the Diamond.

Pavilion Height: The 43.1% percentage is of the diameter of the Diamond.

Crown Angle: The 34.5 degree angle of the crown is measured from the horizontal girdle.

Pavilion Angle: The 40.75 degree angle of the pavilion is measured from the horizontal girdle.

Table Diameter: Tolkowsky believed the best size to cut the table facet was 53%. However, today this varies from 54% to approximately 69% depending on the preference of the consumer. A bigger table facet will return more brilliance to the wearer as it allows more light into the gem, but a smaller table allows for bigger crown facets which provide more fire and dispersion. If the table facet goes above 69%, the cutting will be downgraded to 'fair' on the GIA certificate (the GIA grades for cut quality are 'excellent', 'very good', 'good', 'fair' and 'poor').

The modern Round Brilliant Cut consists of 58 facets (or 57 if the culet is excluded). Click the button below to explore our wide range of Diamond jewelry designs and see Round Brilliant Cut at its very best.