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150 Ashley Road, Hale,

Cheshire, WA15 9SA

0161 233 9977


3 Hardman Sq, Spinningfields,

Manchester, M3 3EB

0800 080 3535


5 St Christopher’s Pl, Marylebone,

London, W1U 1NA

020 33 271 271

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Diamond Shapes

Round Brilliant Cut Diamonds Guide

Learn more about the ideal cut - the most popular shape for engagement rings.

Round Brilliant Cut Diamond Shape

The round brilliant cut diamond is the most popular diamond ring shape and the most advanced cut in regards to light performance, proportions and symmetry and is referred to as the ideal cut or American Ideal cut. The cut was first invented in 1919 by Marcel Tolkowsky, who was a mathematician and gemologist.

The diamond has 58 facets and the best proportions and symmetry, maximising the fire and brilliance of the diamond. 33 of its facets are placed on the stone’s crown and the other 25 are located on the diamond pavilion.

Steven Stone recommends buying Round Brilliant cut diamonds with table percentage between 55 and 60% and depth between 59% and 62.5% of the stone’s total diameter.

From all diamond shapes, the round cut has the best fraction and sparkle. This allows more flexibility in the cut, colour, clarity and carat weight of the stone.

Diamond Ratio

These are the recommended ratios, table% and depth% for round brilliant cut diamonds.

Shape Length To Width Ratio Table% Depth%
Round Brilliant N/a 55% – 60% 59% – 62.5%

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