Understanding Diamond Proportions: Fancy Cut Diamonds

Fancy cut – any shape other than a round brilliant; Asscher, Emerald, Heart, Oval, Pear, Marquise, Princess, Radiant

When grading fancy cut diamonds often times the overall look of the stone is more important than all the proportion details you would look for in a round brilliant. Color and symmetry are still very important, but your eye and personal taste will ultimately determine if the diamond is beautiful.   For fancy cuts, there is no worldwide consensus about beauty.

There are three main cutting styles (the arrangement of the diamond’s facets) for

Fancy cuts; brilliant cut, step cut, and mixed cut.  The most popular cutting style is the brilliant cut.

Brilliant cut – a cutting style where triangular and kite shaped facets start at the diamond’s center and go outwards towards the girdle (example – Oval shape diamond)

Step cut – a cutting style with long, narrow, four sided facets cut in rows parallel to the girdle on both the crown and pavilion (example – Emerald shape diamond)

Mixed cut – a cutting style that combines the step cut and brilliant cut (example – Princess shape diamond)


Table, Crown, and Girdle


For fancy cuts, graders measure the table width and stone width then calculate table percentage.  Brilliant fancy cuts are measured from the belly (slight curving center of the long side of a Pear, Heart, Oval, and Marquise) bezel facets.  Step cuts are measured in the middle of the stone because the facets are not always parallel and this measurement provides consistent results.

The following formula is used to calculate table percentage:  Table width divided by stone width x 100 = table percentage rounded to the nearest one percent.  Large tables are common for fancy shape diamonds.


Crown angles are estimated for fancy cuts diamonds.  To obtain the estimate, graders look along the length of the stone’s profile.  For brilliants, graders examine the bezel facets at the belly and for step cuts, graders examine the profile of the middle row of facets.

Unlike round brilliant cut diamonds where a numerical value is applied to the crown angle, a fancy cut diamond’s crown angle is listed as acceptable, slightly shallow, very shallow, slightly steep, and very steep.


Girdle thickness for fancy cut diamonds is evaluated in the same manner as it is for round brilliants however, allowances must be made.   For example, when evaluating girdle thickness for a heart shape diamond the cleft and point will have a thicker girdle than the rest of the stone because of the shape.

Pavilion Depth

To evaluate pavilion depth, graders consider three main factors; face-up appearance, total depth percentage, and the relationship between crown height to pavilion depth.   To determine a final assessment of the diamond, graders consider all of these things individually then together.

First, graders look at the stone face up to determine the stone’s brilliance.  The appearance will determine if the pavilion is steep or shallow.  If the stone looks glassy or if the girdle’s reflection can be seen at the sides of the table the pavilion is most likely shallow and if the stone looks dark the pavilion is most likely steep.

After evaluating face up appearance, graders consider the total depth percentage.  This is the diamond’s depth from the table to the culet and is expressed as a percentage of the width.

The following formula is used to determine total depth percentage:  Stone depth divided by stone width x 100 = total depth percentage

The normal range for total depth percentage is 55% to 65%.  If the total depth percentage falls outside the range graders will begin to evaluate other proportions.  If the stone is deep, graders will look for a high crown, thick girdle, or deep pavilion.  If the stone is shallow, graders will look for a thin crown, thin girdle, or shallow pavilion.  Note – even if the diamond has a total depth percentage within the normal range it is still important to examine each component of the diamond.

To evaluate pavilion depth, graders look at the profile of the diamond and compare the crown height to the pavilion depth.  A well-proportioned diamond’s pavilion should be approximately 2.5 to 4.5 times the depth of the crown.

Bow-Tie and Pavilion Bulge

The final step in evaluating the pavilion is the bow–tie effect and pavilion bulge.  The bow-tie effect is a dark area across the center of an elongated brilliant cut.  When viewing the diamond face up the bow-tie will be visible in all stones however, this should be faint and not dark.   Pavilion bulge is the outward curve of the pavilion facets on a step cut diamond.  Cutters will sometimes cut the top row of pavilion facets wide and at a steep angle.  This creates a bulge and increases weight, which in turn causes light leakage and can make the stone difficult to set.

Culet Size

Culet size is graded in the same manner for fancy cuts as it is for round brilliants.  In fancy cuts the culet is sometimes elongated so the grader will only consider the culet’s width as a factor in its size.

Shape Appeal (“Eye-pleasing”)

Shape appeal is not the same as symmetry.  Shape appeal is what shape is pleasing to your individual eye.


When determining symmetry all of the diamonds parts are compared to its whole.   Symmetry = balance.  To have good symmetry a diamond’s parallel parts should be the same size and shape from the face up and profile view.  (Example – both lobes on a heart shape diamond should be the same size and shape)

Length to Width Ratio

Length to width ratio is a characteristic of fancy cuts and is an aspect of shape appeal.  Length to width ratio is the relationship between the length and width of the diamond.  Certain ratios are more “eye pleasing” than others.   To calculate the ratio you will need the length and width of the stone.  Once those numbers are determined, you divide length by the width and round to the nearest hundredth.  That becomes the first number in the ratio with the width always being one.

The formula for length to width ratio is as follows:  Stone length divided by the stone width

Example: Using an Oval with a length of 9.00mm and a width of 6.00mm

9.00mm divided by 6.00mm = 1.50

The length to width ratio is 1.50:1

Shop all Since 1910 fancy cut diamonds and engagement rings to find the perfect one for you

Buyers Guide: How To Purchase Diamonds

Buying a diamond should be a great experience and one that is not confusing or overwhelming.  Like any other large purchase you make, education and knowledge is key.  Before purchasing your diamond make sure you have at least a basic understanding of the 4Cs, diamond shapes, diamond terminology, and what to look for on a diamond grading report.  This will prepare you to ask the right questions and will give you the confidence that the decision you make is the right one for you.

The 4Cs of Diamonds: Cut, Clarity, Carat Weight, Color

Diamond Cut

Of the 4Cs, Gemologists believe that cut has the greatest influence on a diamond’s beauty.  Cut is the factor that determines the diamond’s fire, sparkle, and brilliance.   Diamonds have a unique ability to effectively manipulate light.  This unique quality can only be realized with an extremely high level of accuracy during the cutting and polishing process.  Where nature dictates the uniqueness of color and clarity, humans affect the cut.  While cutting diamond rough, cutters must not only consider the proportions of a diamond, but also the craftsmanship of overall symmetry and polish as well.

A diamond’s brilliance comes from light entering the crown and reflecting from one facet to another and returning back out the crown.  A diamond that is cut too shallow or too deep will not reflect light properly and the diamond will not be as brilliant as a diamond with an excellent cut.

Diamond Clarity

Clarity refers to the absence of clarity characteristics in the diamond. The GIA clarity scale consists of 11 grades ranging from flawless to included.  When determining a diamond’s clarity grade, GIA considers the size, nature, color, position, and quantity of clarity characteristics under 10x magnification.  The lesser the number of inclusions or blemishes a diamond has the higher clarity grade it will receive.  A diamond with no inclusions using 10x magnification will be considered flawless and is very rare and more costly.


An inclusion is a clarity characteristic either totally enclosed in a polished diamond, reaching or extending into it from the surface, or one that is caused by treatments or the cutting process.  Note – Inclusions caused by treatments or the cutting process may not always be documented on the diamond certificate.


A blemish or external clarity characteristic is on the surface of the diamond only and can be caused by wear, the cutting process, or may be a result of the diamond’s crystal structure.   Blemishes play a lesser role than inclusions do when determining the clarity grade, but may affect the polish grade.

GIA Clarity Grades

FLFlawless – no blemishes or inclusions under 10x magnification.

IFInternally flawless – no inclusions and only very minor surface blemishes.

VVS1 and VVS2 Very, very slightly included – very, very small microscopic inclusions extremely difficult to see under 10x magnification.

VS1Very slightly included – very small microscopic inclusions difficult to see under 10x magnification.

VS2Very slightly included – very small inclusions somewhat easy to see under 10x magnification.  These diamonds represent a good value to someone looking for a high quality diamond, as the very small imperfections do not affect the beauty of the diamond.

SI1Slightly included – small inclusions that are easy to see under 10x magnification. This clarity is an excellent choice for someone looking to stay within a budget, but wants a diamond that will look as good as a higher clarity diamond except when viewed under magnification.

SI2 – Slightly included – small inclusions that are visible under 10x magnification. Depending on their location within the diamond, they may sometimes be visible to the unaided eye without magnification.  SI2 diamonds are attractively priced and typically no visible difference can be seen without magnification.  If you are interested in an SI2 diamond and would like us to personally verify if it is eye-clean, please give us a call at 1-800-979-1910.

I1* and I2Included – imperfect with inclusions that are obvious to the unaided eye and may affect the diamond’s durability.

I3*Included – imperfect with inclusions that are extremely obvious to the unaided eye and pose a definite threat to the diamond’s durability.

*At Since1910.com, we do not sell I1, I2, and I3 clarity diamonds.

Diamond Carat Weight

Carat weight refers to the size of the diamond.  Carat is the standard term used for the weight of a diamond and received its name from the seed of a carob tree.  The carob seeds were used by early diamond traders on scales as units of weight for small amounts of diamonds because of their consistent size.  The weight of the carob seed was 200 milligrams and the weight of a carat is exactly 200 milligrams or as it is know today, 0.2 grams

Many believe that the term carat represents the size of the diamond however; carat represents the weight of a diamond.  One carat is divided into 100 points.  So, for example, a quarter carat or 25 point diamond weights .25 carats (cts).   Diamonds weighing over one carat are expressed as carats and decimals.   They are measured to the hundred thousandths of a carat and rounded to a hundredth of a carat.   For example, a 1.25 stone would be described as one point twenty five carats.

The cost of a diamond is not measured in weight alone.   Several diamonds of the same weight can be priced considerable different.  When calculating the cost of any diamond, clarity, cut, and color are major factors as well.

Diamond Color

Color refers to the absence of color in the diamond.  Diamonds composed of pure carbon are colorless and extremely rare and costly.  Most diamonds contain nitrogen, boron, or hydrogen all of which impact color.  A majority of white diamonds sold on the market today contain traces of nitrogen, which causes slight shades of yellow or brown.  Small, subtle differences in color can make a substantial difference in a diamond’s value.

In a effort to eliminate confusion related to diamond color, the Gemological Institute of America (GIA) implemented the color grading system in the 1950s which is still being used industry wide today.   Diamonds are graded on a scale beginning with the letter D (colorless) and ending with Z (light yellow or brown).   When creating the new color scale GIA chose to start with the letter D as a means of starting over.  Prior to GIA implementing the D-Z scale, other systems all of which were inconsistent and inaccurate, already used the letters A-C, numbers 0-3, and the Roman numerals I-III.  It is important to note that diamonds at the end of the color range with a noticeable yellow tinge are not considered fancy yellow color diamonds.

Factors to Consider When Choosing a Diamond Color

  • When a diamond is well cut the diamond’s refraction and dispersion will often disguise certain degrees of color and may make a darker diamond appear whiter when viewed with the unaided eye (without magnification).
  • The size of the diamond will also affect the appearance of its color.  Color can easily be seen in larger diamonds as opposed to smaller diamonds.  Often times it is difficult to see color in diamonds under a 1/2 carat with the unaided eye.
  • The shape of the diamond will affect its color as well particularly step cut diamonds such as the Asscher and Emerald that have large open facets and do not display the brilliance of other cuts.  The center of these diamonds display a “window effect” where some of the color in the diamond can appear washed out and make it appear whiter then its actual color grade.  The shallower the cut of the diamond the more apparent this will be.

Diamond Shapes

Diamond shape is the basic outline of the diamond.   Here are some popular shapes sold today.

Round Brilliant is the most popular.  It consists of 56 to 58 facets and displays the most brilliance, fire, and scintillation of all diamond cuts on the market today.

Asscher is a stepped square cut also known as the modified square emerald cut.  It consists of 72 facets and resembles the shape of an octagon.

Cushion is not as brilliant as many of the more modern cuts, but has a classic romantic look that definitely stands out in a crowd.

Emerald is a cut that provides a very elegant classy look and is known for its long lines.  The pavilion is cut with large rectangular facets to create an open effect or optical appearance.

Heart is known as the most romantic of all shaped diamonds.  The heart consists of 59 facets and is essentially a pear cut with a cleft at the top.

Marquise resembles the shape of a football when viewed from above.  The marquise is bright, clear, and has a great deal of sparkle.

Oval is an adaptation of the round brilliant and usually looks larger than the round brilliant of the same carat weight.

Pear is half oval and half marquise.  The pear has 58 facets and displays the brilliance, fire, and sparkle of the round brilliant.

Princess is square shaped with uncut pointed corners.  The princess has 58 facets and is known for its brilliance, fire, and sparkle.

Radiant has 70 facets and has the brilliance and fire of the round brilliant.  The radiant is square/rectangle in shape with cropped corners.

Diamond Certificates

A diamond certificate (aka – diamond plot, diamond grading report) is a document certifying a diamond is genuine and is created by a group of gemologists after the diamond is carefully evaluated.  The report contains information such as carat weight, color, clarity, proportions, and a cut grade for round diamonds.   The certificate also contains a “blueprint” of the diamond’s clarity characteristics.

To understand all aspects of the diamond grading report, click on the GIA link below:


To understand all aspects of the diamond anatomy, click on the GIA link below:



Understanding Diamond Symmetry

The details of a diamond’s cut are referred to as its finish.  Finish is made up of two categories; Symmetry and Polish.  Symmetry is the exactness of the shape and placement of a diamonds facets and polish is the overall condition of the facet surfaces.

Almost all diamonds on the market today have some minor symmetry problems; which are usually not visible to the unaided eye and have very little effect on a diamond’s appearance and beauty.

To evaluate symmetry, gem laboratories consider the evenness of a diamond’s outline and the size, shape, and placement of its facets.  For grading purposes, two types of symmetry are considered; proportion symmetry and facet symmetry.  Proportion symmetry is the alignment and balance of the diamond’s table, culet, girdle, and angles while facet symmetry is the shape, placement, and presence or absence of the facets themselves.  Proportion symmetry and facet symmetry make up the diamond’s symmetry rating.

Before assigning a symmetry grade, GIA and other gem laboratories look for symmetry variations under 10x magnification.  A diamond’s symmetry grade and the abbreviation of the symmetry characteristic are listed on all diamond grading reports.

The GIA symmetry grades are: Excellent (E), Very Good (VG), Good (G), Fair (F), and Poor (P)

The AGS symmetry grades are: Ideal (AGS 0), Excellent (AGS 1), Very Good (AGS 2), Good (AGS 3, 4) Fair (AGS 5, 6, 7), and Poor (AGS 8, 9, 10)

Common Variations in Proportion Symmetry

Crown angle variation (CV)

Culet off-center (C/oc)

Extra facets (EF)

Girdle thickness variation (GTV)

Misalignment of crown and pavilion facets (Aln)

Misshapen facets (Fac)

Missing facet (MF)

Non-pointing (Ptg)

Out-of-round girdle outline (OR)

Pavilion angle variation (PV)

Table off-center (T/oc)

Table/culet alignment (T/C)

Table and girdle not parallel (T/G)

Wavy girdle (WG)

Excellent and Very Good symmetry grades are rare.  Diamonds with a symmetry grade of Good offer exceptional beauty and are the most frequently purchased diamonds today.  Diamonds with a high symmetry grade are more important in diamonds that have very high clarity grades such as flawless or internally flawless than diamonds with a lower clarity grade.  Symmetry is important for both round brilliant cut diamonds as well as fancy cut diamonds.

When budget allows, Since 1910 recommends purchasing a diamond for an engagement ring with a symmetry grade of Good or higher.

To learn more about diamonds, visit our diamond education section.

diamond symmetry chart

What is a Fancy Cut Diamond?

A fancy cut diamond is any diamond shape other than a round brilliant.  The most popular fancy cut diamonds sold today are asscher cut, cushion cut, emerald cut, heart shaped, marquise shaped, oval shaped, pear shaped, princess cut, and radiant cut, but there are many others.

The face up shape of a fancy cut diamond is usually the first thing people notice and the main reason why they are purchased.  Fancy cut diamonds provide a way for you to express your individuality and appeal to those looking for that less traditional look.  Fancy cut diamonds are also a great choice as side stones for a three stone engagement ring or accent stones on a solitaire setting.

Each fancy cut diamond has its own characteristics, so you should take the time to familiarize yourself with each.  Most fancy cut diamonds on the market today are cut using the brilliant cut facet arrangement allowing for the same brilliance, fire, and scintillation of that of the round brilliant cut diamond, but some are cut using step cuts or mixed cuts.  The round brilliant cut features triangular and kite shaped facets that begin at the diamond’s center and go out to the girdle.   A step cut has long, narrow, four sided facets arranged in rows parallel to the girdle on both the crown and pavilion.  Mixed cuts are a mix of both the round brilliant and step cuts.  They can either have brilliant cuts on the crown and step cuts on the pavilion or step cuts on the crown and brilliant cuts on the pavilion.

fancy cut diamond

Some Diamond Terms for Fancy Cuts

Belly – the center area of the side of a heart, marquise, oval, or pear where it curves out slightly.

Head – the rounded end of a pear

Shoulders – the curved edges between the head and belly of a pear

Lobes – the rounded part of a heart

Cleft – the v-shaped part of a heart

Symmetry and length-to-width ratio are important factors to consider when purchasing fancy cuts.  You always want a fancy cut that is symmetrical.  For example, both lobes of a heart should be the same size, both ends of an emerald should be the same width.  Length-to-width ratio determines the shape of a fancy cut.  There are preferred ranges for each shape, but this is also a personal preference.

To learn more about the characteristics of each fancy cut diamond visit our diamond education section.