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Cut Grading Classification
Cut Grading Classification

Cut Grading Classification


Currently most laboratories only provide cut grading for round diamonds as it is harder to assess the ideal proportions for fancy shape diamonds. The only laboratory that currently provides cut grades for fancy shaped diamonds is the less well known AGS, which introduced a Princess cut grade in 2005 and an Emerald cut grade in late 2006.

Based on existing values for the round brilliant and extensive research, We have devised a table of recommended proportions for fancy shapes below. Please note these values are only to be used as a reference or guideline. We have grouped the shapes according to their cut classification type (brilliant, modified brilliant, step and mixed cut).



Cut Classifications

Cut Classifications.



Round Brilliant Cut


Round Brilliant Cut

Round Brilliant Cut.



The round brilliant is the most brilliant of all diamond cuts. Brilliant cuts were first developed by Marcel Tolkowsky (1899-1991) who came from a Belgian family of diamond cutters, and derived the cut from mathematical calculations that maximised the brilliance and dispersion of light.

Since its creation in the early twentieth century, the round brilliant cut has become the most researched and popular of all cuts. It is comprised of 58 facets and naturally follows the crystal shape of a rough diamond therefore designed to give maximum scintillation, beauty and fire. The simplest cut is a single cut, a form of cutting a round diamond with only 18 facets. In the 1980s in Japan, it was discovered that a round brilliant diamond with exceptional symmetry, when viewed through a special viewer displayed a pattern of hearts and arrowheads.

Based on our experience, grading classifications from most grading laboratories translate roughly to the table below:


Round Brilliant Cut


Round Cut Grading Classification Excellent Very Good Good Fair Poor
Depth % 60 to 63 58 to 64 57 to 65 56 to 67 >56 or <67
Table % 53 to 58 52 to 62 51 to 65 50 to 67 >56 or <67
Symmetry Very good to excellent Good to excellent Good to excellent Fair to Excellent Poor to Excellent
Polish Very good to excellent Good to excellent Good to excellent Fair to Excellent Poor to Excellent
Crown Angle 34 to 35 32 to 36 30 to 38 29 to 41 <29 or >41
Pavilion Depth 42 to 44 42 to 44 41 to 46 39 to 48 <39 or >48
Girdle Thin to Sl. Thick Very Thin to Sl. Thick Very Thin to Thick Very Thin to Very Thick Ex. Thin to Ex. Thick
Culet None Very Small Small Medium > Medium
L/W Ratio 1.00 to 1.01 1.00 to 1.01 1.00 to 1.01 1.02 > 1.02


Modified Brilliant Cuts


Any style of diamond cutting other than the round brilliant or single cut is called a fancy cut, or fancy shape. The cuts that have been developed based on the original round brilliant design are known as modified brilliant cuts. Modified brilliants include the Princess, Marquise, Oval, Pear, Heart and Trillion cuts.

Princess Cut


Princess Cut Grading Classification Excellent Very Good Good Fair Poor
Depth % 62 to 73 60 to 77 57 to 83 55 to 84 >56 or <84
Table % 57 to 72 55 to 75 54 to 80 52 to 85 >52 or <85
Symmetry Good to excellent Good to excellent Good to excellent Fair to Excellent Poor to Excellent
Polish Good to excellent Good to excellent Good to excellent Fair to Excellent Poor to Excellent
Girdle Very Thin to Sl Thick Very Thin to Sl Thick Very Thin to Thick Very Thin to Very Thick Ex. Thin to Ex. Thick
Culet Very Small Very Small Small Medium > Medium
L/W Ratio 1.00 to 1.03 1.00 to 1.03 1.04 to 1.05 1.06 to 1.08 > 1.08


The ideal proportions of table and depth are much higher for a Princess than for a round brilliant cut. On a GIA certificate, the technical name for a Princess cut is a modified square- or rectangular brilliant cut. It can have the same number of facets as a round diamond (57), but may have as many as 76 or even up to 144.


Radiant Cut


Radiant Cut Grading Classification Excellent Very Good Good Fair Poor
Depth % 62 to 68 58 to 70 57 to 75 56 to 80 >56 or <80
Table % 58 to 65 56 to 70 54 to 75 53 to 79 >53 or <79
Symmetry Good to excellent Good to excellent Good to excellent Fair to Excellent Poor to Excellent
Polish Good to excellent Good to excellent Good to excellent Fair to Excellent Poor to Excellent
Girdle Very Thin - Sl Thick Very Thin - Sl Thick Very Thin to Thick Very Thin to Very Thick Ex. Thin to Ex. Thick
Culet None Very Small Small Medium > Medium
L/W Ratio Square 1.00 to 1.03 1.00 to 1.03 1.04 to 1.05 1.06 to 1.08 > 1.08
L/W Ratio Rectangle 1.20 to 1.30 1.10 to 1.40 1.10 to 1.40 1.08 to 1.50 < 1.08 or > 1.50


There are diverse preferences when it comes to shape in radiant cut diamonds, from a perfectly square 1.00 length to width ratio (any ratio of 1.05 or less will appear square to the naked eye), to a more traditional rectangle. The rectangular radiant cut is an excellent option for buyers who like the emerald cut shape, but want something with the brilliance of a round. The square radiant looks very similar to a princess cut, but with cropped corners. Once set, a square radiant and a princess look virtually identical, since the prongs cover the corners.


Oval Cut


Oval Cut Grading Classification Excellent Very Good Good Fair Poor
Depth % 58 to 64 57 to 66 56 to 68 46 to 71 >46 or <71
Table % 55 to 62 53 to 64 52 to 65 50 to 70 >50 or <70
Symmetry Good to excellent Good to excellent Good to excellent Fair to Excellent Poor to Excellent
Polish Good to excellent Good to excellent Good to excellent Fair to Excellent Poor to Excellent
Girdle Very Thin - Sl Thick Very Thin - Sl Thick Very Thin to Thick Very Thin to Very Thick Ex. Thin to Ex. Thick
Culet None Very Small Small Medium > Medium
L/W Ratio 1.35 to 1.50 1.30 to 1.55 1.25 to 1.60 1.20 to 1.65 > 1.20 or < 1.65


Pear Cut


Pear Cut Grading Classification Excellent Very Good Good Fair Poor
Depth % 58 to 64 57 to 66 56 to 68 46 to 71 >46 or <71
Table % 55 to 62 53 to 64 52 to 65 50 to 70 >50 or <70
Symmetry Good to excellent Good to excellent Good to excellent Fair to Excellent Poor to Excellent
Polish Good to excellent Good to excellent Good to excellent Fair to Excellent Poor to Excellent
Girdle Very Thin - Sl Thick Very Thin - Sl Thick Very Thin to Thick Very Thin to Very Thick Ex. Thin to Ex. Thick
Culet None Very Small Small Medium > Medium
L/W Ratio 1.45 to 1.55 1.40 to 1.65 1.35 to 1.80 1.25 to 2.00 > 1.25 or < 2.00


Heart Cut


Heart Cut Grading Classification Excellent Very Good Good Fair Poor
Depth % 52 to 60 50 to 62 45 to 65 40 to 69 >46 or <71
Table % 55 to 62 50 to 62 52 to 65 50 to 70 >50 or <70
Symmetry Good to excellent Good to excellent Good to excellent Fair to Excellent Poor to Excellent
Polish Good to excellent Good to excellent Good to excellent Fair to Excellent Poor to Excellent
Girdle Very Thin - Sl Thick Very Thin - Sl Thick Very Thin to Thick Very Thin to Very Thick Ex. Thin to Ex. Thick
Culet None Very Small Small Medium > Medium
L/W Ratio 0.95 to 1.02 0.89 to 1.05 0.83 to 1.10 0.80 to 1.15 >0.80 or < 1.15


Marquise Cut


Marquise Cut Grading Classification Excellent Very Good Good Fair Poor
Depth % 58 to 64 57 to 66 56 to 68 46 to 71 >46 or <71
Table % 55 to 62 53 to 64 52 to 65 50 to 70 >50 or <70
Symmetry Good to excellent Good to excellent Good to excellent Fair to Excellent Poor to Excellent
Polish Good to excellent Good to excellent Good to excellent Fair to Excellent Poor to Excellent
Girdle Very Thin - Sl Thick Very Thin - Sl Thick Very Thin to Thick Very Thin to Very Thick Ex. Thin to Ex. Thick
Culet None Very Small Small Medium > Medium
L/W Ratio 1.85 to 2.00 1.75 to 2.15 1.65 to 2.30 1.55 to 2.45 >1.55 or < 2.45


Beyond the most popular Princess cut, Modified Brilliants come in a range of other shapes. The Radiant cut, which can be square or rectangular usually comes with 70 facets, whilst the Oval (which is in effect an elongated round) often has 58 facets. Other shapes include a tip formation such as the Pear shape (56-58 facets), Heart Shape (usually 56-58 facets), and Marquise (56-58 facets).

Other factors to take into account for Modified Brilliant Cuts include:

Bow tie effect: Some fancy shape diamonds have two black triangles across the middle of the diamond that look like a bow tie. Although bow ties are normal in some fancy shapes, a bow tiethat is too big diminishes a diamond's beauty. Depending on the size, angle and placement of the diamond's facets, this bow tie can be barely visible ('minimal') or very pronounced. It occurs from the variations in the pavilion facet angles which are longer than they are wide which results in a small amount of light leaking through the diamond. Facets are suppose to alternate between light and dark as the diamond, viewer or light source are moved but with the bow tie effect, certain facets stay relatively dark regardless of the movement.

Girdle Thickness: Girdle width varies considerably more in fancy shapes than in the round brilliant. For example, the marquise, pear and heart cuts shapes tend to have thick girdles or are extremely thick at the tips, or in the cleft of the heartshape. The princess cut, on the other hand, which has square corners, may have an extremely thin girdle. It is generally recommended to avoid extremely thin or thick girdles to avoid chipping at one extreme and retaining excessive weight to the detriment of the size of the diamond.


Step Cuts


Emerald Cut


Emerald Cut Grading Classification Excellent Very Good Good Fair Poor
Depth % 58 to 65 55 to 70 52 to 75 50 to 80 >50 or <80
Table % 60 to 65 59 to 70 56 to 75 53 to 79 >53 or <80
Symmetry Good to excellent Good to excellent Good to excellent Fair to Excellent Poor to Excellent
Polish Good to excellent Good to excellent Good to excellent Fair to Excellent Poor to Excellent
Girdle Very Thin - Sl Thick Very Thin - Sl Thick Very Thin to Thick Very Thin to Very Thick Ex. Thin to Ex. Thick
Culet None Very Small Small Medium > Medium
L/W Ratio Square 1.00 to 1.03 1.00 to 1.03 1.04 to 1.05 1.06 to 1.08 > 1.08
L/W Ratio Rectangle 1.40 to 1.50 1.30 to 1.60 1.20 to 1.80 1.15 to 1.90 < 1.15 or > 1.90


Emerald cut diamonds vary from nearly square to a narrow rectangle. The classic emerald cut diamond has a length to width ratio of around 1.50. If you prefer the look of the square emerald cut diamond, be sure to consider the asscher cut as well (which has a very similar appearance, and is defined by GIA as a square cut emerald).


Asscher Cut


Asscher Cut Grading Classification Excellent Very Good Good Fair Poor
Depth % 58 to 65 55 to 70 52 to 75 50 to 80 >50 or <80
Table % 60 to 65 59 to 70 52 to 75 50 to 80 >50 or <80
Symmetry Good to excellent Good to excellent Good to excellent Fair to Excellent Poor to Excellent
Polish Good to excellent Good to excellent Good to excellent Fair to Excellent Poor to Excellent
Girdle Very Thin - Sl Thick Very Thin - Sl Thick Very Thin to Thick Very Thin to Very Thick Ex. Thin to Ex. Thick
Culet None Very Small Small Medium > Medium
L/W Ratio 1.00 to 1.03 1.00 to 1.03 1.04 to 1.05 1.06 to 1.08 > 1.08


Step cuts mainly include the Emerald and Asscher cuts. They have sloping, four-sided facets that are cut below the table and run parallel to the diamond's girdle. Their corners are generally cut, as square corners would be weaker and could cause the diamond to fracture. The advantage of step cuts is that they preserve more of the weight of the raw diamond than brilliant cuts, however they can also make inclusions and flaws appear more obvious. Because both the pavilion and crown are comparatively shallow, step cut stones are generally not as bright or fiery as brilliant cut stones, but they do accentuate a diamond's clarity and give the diamond a less cluttered and a purer or more transparent appearance.

Because of the transparency, cut grades for step cuts are generally considered less important than for brilliant cuts.

Mixed Cuts (Cushion Cuts)



Cushion Cut


Cushion Cut Grading Classification Excellent Very Good Good Fair Poor
Depth % 62 to 68 58 to 70 57 to 75 56 to 80 >56 or <79
Table % 58 to 65 56 to 70 54 to 75 53 to 79 >53 or <79
Symmetry Good to excellent Good to excellent Good to excellent Fair to Excellent Poor to Excellent
Polish Good to excellent Good to excellent Good to excellent Fair to Excellent Poor to Excellent
Girdle Very Thin - Sl Thick Very Thin - Sl Thick Very Thin to Thick Very Thin to Very Thick Ex. Thin to Ex. Thick
Culet None Very Small Small Medium > Medium
L/W Ratio Square 1.00 to 1.03 1.00 to 1.03 1.04 to 1.05 1.06 to 1.08 > 1.08
L/W Ratio Rectangle 1.15 to 1.20 1.10 to 1.30 1.10 to 1.30 1.08 to 1.50 < 1.08 or > 1.50


While the classic cushion cut diamond is a square (with a length to width ratio of 1.00), they are often found in slightly rectangular shapes as well. The most popular shape is a slight rectangle of 1.10-1.20 length to width, however personal preference should dictate choice.

The cushion cut is the most common mixed cut, combining faceting elements from both the modified brilliant and step cuts allowing it to ensure weight preservation from the step cuts while at the same time enjoying the optical effects of brilliants. Typically the crown is fashioned like a brilliant cut and the pavilion more like a step cut. Although mixed cuts are all relatively new, dating back to the 1960s, the cushion shape is much older.

The cushion is one of the least uniform cut diamonds and comes in many different variations. In general we can separate the cut into two categories, the cushion brilliant cuts and the cushion modified brilliant cuts.



Cushion Cut Types

Cushion Cut Types.



Vintage Cuts


There are also a number of vintage diamond cuts which remain popular as classic styles and can be described as follows.

Old Mine Cut - This is a square diamond cut with gently rounded corners and brilliant-style facets. The crown is typically high but table is small, and the culet is big enough to be visible through the top of the stone.

Old European Cut - This is a square diamond cut with gently rounded corners and brilliant-style facets. The crown is typically high but table is small, and the culet is big enough to be visible through the top of the stone.

Rose Cut - As the name suggests, this cut's brilliant-style facets are arranged in groups that make the diamond look like an opening rose bud. The rose cut is usually made up of 12 or 24 triangular facets reaching up to form a point, a crown that rises from its base and has no pavilion. Developed prior to the use of electric lighting, rose cuts lost their popularity in the early 20th century due to their lack of brilliance.



Vintage Cuts Types

Vintage Cuts Types.