PL 18K 18K 18K 9K 9K 9K PA PL 18K 18K 18K 9K 9K 9K PA Length: 4.37mm Length: 4.37mm Width: 4.35mm

Round Brilliant Cut Diamonds

Round Brilliant Cut Diamonds

Around three-quarters of all diamonds sold are Round Brilliant - this shape is renowned for its unrivalled fire and brilliance.

Round Brilliant Cut Diamond Top View

Round Brilliant Cut Diamond (Top View)

Round Cut Diamond Side View

Round Brilliant Cut Diamond (Side View)

Outline Circular
Cutting Style Brilliant
Description A round stone cut for maximum fire, brilliance and scintillation
No. of Facets 57
Ideal L/W Ratio 1.0


Simple, classical, beautiful - the round brilliant is the diamond equivalent of a rose. 

The angle of every facet has been precisely calculated to reflect the most light, creating a stunning, scintillating display from even the smallest amount of movement. Its simple elegance needs no fancy setting, which is why the single-round brilliant solitaire continues to be the most popular style of engagement ring

We Say

If in doubt, choose a Round Brilliant. You can’t go wrong with this stunning and classic shape.


Just because a diamond is round doesn't make it brilliant. A brilliant-cut is defined as one resembling two pyramids placed base to base, intended to enhance the gem’s sparkle with the least possible sacrifice in carat weight. 

The Round Brilliant diamond shape has 57 facets comprising 33 facets 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. There may also be a culet.

Round Brilliant Cut Diamond Top View

Round Brilliant Cut Diamond (Top View)

Round Cut Diamond Side View

Round Brilliant Cut Diamond (Side View)

Shop loose round-cut brilliant diamonds

Round Brilliant diamonds most closely follow the natural contours of rough diamond crystals. This means less cutting is required to shape the stone which results in less waste and higher carat weight. This is one reason why Round Brilliant diamonds offer excellent value for money.


All independent laboratories have measurable criteria for certifying the cut grade of a Round Brilliant diamond. These vary slightly from lab to lab but typically they include a combination of depth, table, crown angle, pavilion angle, crown height, culet size, girdle thickness, polish, symmetry and many other factors. We use this independently certified cut grade for all the Round Brilliant diamonds we supply.


Research suggests the Round Brilliant shape has its roots in 15th Century Belgium where the first ‘brilliant’ cut is said to have originated. Later, Vincenzio Perruzzi, a 17th Century Venetian lapidary, doubled the number of crown facets from 17 to 33. However, it wasn't until the 20th Century that diamond-cutting technology was advanced enough to precisely engineer the beautifully proportioned Round Brilliant. 

In 1919, a Belgian gemmologist and mathematician named Marcel Tolkowsky developed a mathematical formula for cutting and angling facets on diamonds to provide maximum reflected light and optimum brilliance. Tolkowsky was the first to state that diamonds cut too deep or too shallow would allow light to escape out of the sides or bottom of the gem, resulting in a loss of fire and brilliance. The design he developed as part of his doctoral thesis at the University of London formed the basis of the modern Round Brilliant cut found today.


Shop round brilliant diamond rings

The pure, simple beauty of the Round Brilliant is the perfect shape for a stunning pair of diamond earrings and, of course, is the most popular choice for engagement rings.

The Round Brilliant is perfectly proportioned to look good on all finger shapes, although a lower carat-weight diamond will suit smaller hands better.

Shop round brilliant diamond earrings

Length to Width Ratio

For a diamond that’s a perfect circle, look for a stone with a ratio as close to 1.00 as you can get. A couple of points on either side (e.g. 0.98 - 1.02) won’t make a huge difference and might save you some money but be wary of buying a Round Brilliant that deviates outside of this range - not only won’t it look round, but because of the effect on light behaviour, it won’t be as brilliant either. 


As the most popular shape of a diamond, the Round Brilliant gives you the greatest choice of settings by far. Of course, small round diamonds are also set in diamond wedding rings, eternity rings, diamond pendants and diamond bracelets.

Did you know, we can help you design your own custom-designed jewellery, featuring round brilliant diamonds, so why not give us a tinkle, live chat or contact us to find out more?

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