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Diamond Cut Grade: All You Need To Know About Diamond Cut

Diamond Cut Grade: All You Need To Know About Diamond Cut

Shopping for a diamond can be an overwhelming task – you should consider so many different factors. And one of these factors is the diamond cut grade.

But what is the diamond cut anyway, and how is it graded? In this article, we’ll go through the most crucial factor of the diamond’s quality, so without further ado, let’s dive in.

What Is A Diamond Cut?

Simply put, the “diamond cut” refers to how well a gemstone is cut and polished and also how well-proportioned it is – its symmetry and depth. Remember, the diamond cut doesn’t refer to the stone’s shape, such as cushion shape or oval shape

Cut quality directly affects the diamond’s brilliance and overall beauty: A well-cut diamond is luminous – it reflects white and colored light to the viewer’s eyes. A poorly cut stone is, on the other hand, dull and lifeless instead of brilliant and shiny.

Differences in diamond cut heavily impact the stone’s beauty, aesthetic appeal, and value of the stone – it’s the most important of the diamond 4Cs.

The Difference Between Diamond Cut And Shape

While many people confuse these two terms, diamond cut and diamond shape have distinct meanings.

  • Diamond shape refers to the outline or figure of the stone. For instance, round brilliant and pear-shaped refers to the shape of the diamond. 
  • Cut describes the facets, dimensions, symmetry, and reflective qualities of the gem. For example, a heart-shaped diamond may be cut deep or shallow, brilliant or dull. The heart shape remains, while the quality of the cut may differ significantly. 

The finer the diamond’s cut, the greater the brilliance and sparkle of the stone.

Related Read: Which Diamond Cut Sparkles The Most?

How GIA Grades Cut Quality For Round Brilliant Diamonds

GIA diamond cutting grades for round brilliant diamonds range between Poor and Excellent. Diamond cut grade is based on several factors, including polish, symmetry, brilliance, and fire.

You should only consider round brilliants with an Excellent cut grade for the most beauty and brilliance. Also, make sure the polish and symmetry of the stone are either Excellent or Very Good.

Interestingly enough, 55% of all round brilliant diamonds receive an Excellent cut grade – but around 25-30% of these diamonds are not recommended. Thousands of Excellent cut diamonds actually have lousy specs – and their depth, table, and angles might be off.

That’s why it’s critical to look at the diamond cut grade provided on the GIA grading report and inspect the stone closely yourself or ask a professional for help. 

You wouldn’t want to pay for an Excellent diamond that’s actually only mediocre, would you? 

Diamond Cut Grade Chart

A diamond expert at the GIA reviews each stone under magnification to evaluate the cut grade. Below are the GIA diamond cut grades:

  • Excellent – Diamonds with this grade provide the highest level of brilliance and fire. Since nearly all of the incoming light is reflected through the stone’s table, the diamond radiates with stunning sparkle.
  • Very Good – Stones with Very Good cut grade offer exceptional brilliance and fire. A majority of the incoming light reflects through the stone’s table. Very Good diamonds offer similar brilliance to those stones of Excellent grade.
  • Good – These diamonds provide brilliance, with much of the light reflecting through the stone’s table back to the viewer’s eyes. These stones offer beauty at a lower price tag.
  • Fair – Diamonds with Fair cut grade offer slight brilliance, as light easily leaks through the diamond’s sides and bottom. These stones may be a good option for smaller carats and those playing the role of side stones.
  • Poor – Diamonds with this grade yield almost no sparkle or brilliance; the light that enters the diamond leaks from the sides and bottom of the stone. 

Related Read: What Are The Characteristics Of A Diamond?

How Cut Grade Impacts Price

Diamond cut prices depend on the cut’s precision and quality, mainly symmetry and proportion.

If the diamond’s facets are proportional, they refract and reflect light to the viewer’s eyes in tremendous fashion. Gems that aren’t precisely cut have facets that don’t refract and reflect light in the same stunning manner.

The amount of light return found in a well-cut diamond is always worth the extra price. A stone is less than sparkly without brilliance and fire, no matter the size of the table or carat weight.

The gem’s cut is the quality that most significantly affects the beauty and overall appearance. That’s why the higher diamond-cut prices are always worth every penny – it’s better to spend more on a diamond’s cut than clarity or color.

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Factors Impacting Diamond’s Cut 

The most crucial element of a diamond’s value and the price is its cut quality. Many factors are involved in the cut quality of a diamond, including proportions, facets, finish, and ability to reflect light.

The better these elements are as a whole, the higher the diamond’s quality, and in return, the higher the value. While clarity and color play a role in the gem’s beauty, cut is the most important of the 4Cs.

Here are the main elements that impact the price of a diamond:

  • Proportions (table, depth, width)
  • Symmetrical facets
  • Brilliance (brightness of white light reflection)
  • Scintillation (flashes of sparkle when light moves)
  • Fire (dispersion of colored light)
  • Finishing details (permanent treatment and polishing)

Diamond Proportions 

To further understand the aspects affecting the cut quality, let’s examine the proportions of a diamond, primarily its depth, width, and table. These factors are universally measured and are indicators of a stone’s cut quality.

Diamond cut proportions directly impact a stone’s ability to reflect light and offer brilliance. The actual proportions depend on the ratios between each facet’s angle, size, and shape. Various combinations of said factors affect how the stone will interact with light, determining its beauty and appeal.

The diamond table percentage is assessed by dividing the table’s width by the gemstone’s diameter. For example, if the gem’s table facet is 3.5 mm wide and the stone is 5 mm wide, the table percentage is 70%.

If the diamond’s table percentage is too big, the light won’t get reflected off the gem’s crown. Vibrant reflections of colored light won’t be seen as the light escapes from the diamond’s top instead of reaching the viewer’s eyes.

However, if the table percentage is too low, the light will remain trapped within the stone and be emitted through other sections of the diamond instead of to the viewer’s eyes.

The ideal table percentage depends heavily on the shape of the diamond. If you’re unsure of an excellent table percentage for your stone, don’t hesitate to ask a professional for help.

A diamond’s width is evaluated by measuring from one end of the diamond’s girdle to the other end of the girdle. The width is crucial when evaluating the length-to-width ratio – which signifies how proportionate the stone is along with its intended shape.

Length-to-width ratio is measured by dividing the diamond’s length by its width. For instance, if a gem has a length of 5mm and its width is 3mm, the length-to-width ratio is 1.67.

Depth percentage refers to the diamond’s height, measured from the culet to the table’s top. Depth is measured in millimeters as well as in percentages. The depth percentage is achieved by dividing the depth by the stone’s width.

A lower depth percentage of two stones with identical carat weight will appear more prominent because of the increased width. On the other hand, a depth percentage that’s too low can make a darker appearance as it won’t reflect light as significantly.

Symmetrical Facets

The diamond’s facets are small mirrors that reflect light to the viewer’s eyes. Facets surround the table of the diamond. There are facets below and above the girdle. Also, the pavilion is made up of facets.

The size, symmetry, and placement of the facets affect how well the stone refracts and reflects light. A diamond with unproportioned facets, not enough facets, or too many facets, makes for a less than perfect diamond.


The diamond’s brilliance is the brightness of the white light reflection. 

When viewing the diamond face up under the light, it should reflect a lot of white light. A stone that’s not symmetrical or is cut too shallow or too deep looks dull and lifeless instead of brilliant.


The diamond’s fire is the amount of colored light reflected off the stone’s table. Exceptionally well-cut diamonds not only possess brilliance but stunning fire, as well.

When looking at a gem face-up under daylight, you should be able to see colored light reflecting off of the gemstone. If the diamond doesn’t show the reflection of the colored light, it has a lower amount of fire – meaning it’s not very well-cut.


The flashes of sparkle when the diamond moves – or when the light moves on the stone’s table – is what’s known as diamond scintillation. The scattering of light is caused by the dark and light areas of the gemstone’s surface. 

A diamond with a more significant amount of scintillation is generally more desirable, while the stone that doesn’t exhibit scintillation can appear lifeless.

Finishing Details

The finishing details include its permanent treatment and polishing and are part of the stone’s craftsmanship. The diamond polish refers to the quality of the facet surfaces. 

A well-polished gemstone creates a clear mirror for the light to reflect off – but a diamond with a poor polish job appears dull since the facets don’t reflect the light as vividly.

What If A Diamond Is Cut Too Deep?

When a gemstone is cut too deep, light strikes the pavilion at a sharper angle, leading to the light’s immediate reflection – which is then forced to retract and pass through the diamond’s bottom segment. 

As this happens, light is dulled, resulting in the less vibrant and radiant stone. Even more so, a gem that’s cut too deep usually looks smaller compared to those of an ideal cut.

What If A Diamond Is Cut Too Shallow?

When a stone is cut too shallow, light hits the diamond’s pavilion at a lower angle. The lights traverse through the stone and leave through its sides, instead of reflecting through the stone’s table to the viewer’s eyes.

While shallow-cut gems may appear big based on their table size, the light escape significantly reduces the diamond’s sparkle and brilliance.

Learn More: An In-Depth Guide on Diamond Cutting: How Are Diamonds Cut?

The Diamond’s True Size – Spread

Diamond’s spread is the most straightforward concept for a buyer to grasp: Diamonds with greater spread mean the stone appears bigger.

Interestingly enough, most diamond cut grading systems don’t account for the spread, which is the most accessible cut-related metric to evaluate.

While bigger-looking gemstones aren’t necessarily more brilliant, some people consider them more desirable, and often these diamonds have a premium. Two stones can have an identical carat weight, but one with the more extensive measurements has more spread.

Spread isn’t connected to the diamond’s carat weight, though. It’s the total depth percentage that determines the spread. In general, we recommend stones in the Excellent cut range with the largest measurements so you can get the best of both worlds. 

Sure, you’ll pay a slight premium for this type of diamond – but it’ll be well worth it since you’ll be getting the best of brilliance and size.


So, what does the diamond cut grade refer to, really? 

The diamond cut describes how well a gemstone is cut and polished, and it can be graded on a scale – ranging from Excellent to Poor.

Cut quality directly impacts the beauty and brilliance of the stone – along with its value and price. Generally, we’d recommend going for the Excellent cut grade if you want a diamond that offers maximum brilliance and sparkle.

Remember to examine the stone yourself and check for the specific factors in the grading report before making the purchase. That’s how you ensure you’re getting the best value for your money.

Related Read: Which Diamond Cut Holds Its Value?