Round Brilliant Diamonds

A Guide To Round Brilliant Diamonds


Infamous for its stunning optical properties & timeless classic appearance, the Round Brilliant Diamond is definitely the most popular and well known diamond cuts. Round Brilliants make up over two thirds of all the diamonds sold worldwide.

The predecessor of the Round Brilliant is the Old "European Cut" which was prevalent during the 1900s, and was a very popular diamond choice during the Victorian, Edwardian and Art Deco era.  The Old European Cut had more of a vintage appearance, with a focus on showcasing the Diamonds colour, whereas the Round Brilliant Cut is intended to provide optimum sparkle.

Modern cut design and techniques also mean the least possible loss of rough Diamond during the cutting process. Over time the proportions of the older vintage cuts have changed into their modern counterparts, characterised by smaller culets, wider tables, and more optimised angles and facet shapes. 

In 1919, Marcel Tolkowsky, a Belgian gemologist and mathematician developed a formula for both cutting and angling facets to ensure maximum reflected light and brilliance. Publishing his work “Diamond design”: A study of the reflection and refraction of light in a diamond. The work put forward the ideal dimensions and proportions for a Diamond in terms of reflection and refraction of light. This work formed the basis of the "Brilliant" cut. We also have a more detailed article on Diamond Cut.

The Round Brilliant Cut

The Round Brilliant Diamond follows very specific parameters; it has 57 or 58 total facets (counting or not counting the culet), of which 33 are on the crown and 25 on the pavilion. The crown facets comprise:

  • the table,
  • 8 star facets,
  • 8 kite facets,
  • and 16 upper girdle facets.

The pavilion facets comprise:

  • 16 lower girdle facets
  • and 8 pavilion main facets. 

It is this configuration of facets, along with proportions described by Tolkowskys work that set the parameters for a Round Brilliant:

round brilliant diamond facet configuration

 GIA Diamond Cut Grading

Any Diamond that isn't a Round Brilliant is classed as a Fancy Cut or Shape, and the cut is not graded by the GIA. This doesn't mean that other laboratories or experts won't grade or quantify the Cut of a Fancy.

When buying a Round Brilliant Diamond the ideal is a perfect symmetrical circle, or as close to this as possible. An overly thin girdle should also be avoided as it can be prone to damage.  

solitaire engagement ring with round brilliant diamond

When looking for a setting for a Round Brilliant Cut you are spoilt for choice. A large number of configurations will allow the Diamond to stand out, ideally using 4 prongs to securely hold the centre stone, and an open setting to maximise light exposure. A Solitaire Ring with a Round Brilliant is an ever popular option, but will look just as exceptional in a Halo or Trilogy setting. 

How To Buy A Round Brilliant Diamond - A Video Guide

Go to our Diamond Search Engine and select Round Brilliant in the shape section and see what we currently have available. Alternatively if you need any help Contact Us and we will be happy to answer any queries you may have.