Diamond Cuts Guide: Overview, Grades, Quality and Price


When purchasing a round diamond, focus your choices on “Excellent” cut diamonds (if graded by GIA) or “Ideal” cut diamonds (if graded by AGS). If it’s a different shape that you are purchasing, be sure it comes with an excellent image that you can reliably examine since quality can never be determined purely on certificate stats. For these reasons, it would be safer and better to rely on diamond products from reputable companies like Blue Nile or James Allen.

And if there are any doubts on your part, don’t hesitate to contact us and we will be glad to cater any and all queries and concerns that come to mind.


Diamond Cut does not pertain to the shape of the diamond but to its symmetry, proportioning and polish. For instance, what ratio of the diamond’s diameter is its depth? What are the different angles and how are they symmetrical to each other? I may not be making any sense to you, but these are the crucial aspects that will determine the aesthetic appeal and quality of your diamond.

Simply put, the variations in Diamond Cut will have a significant effect on a diamond’s brilliance, beauty, and overall value.

Here are the essential factors that impact a diamond’s price:

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

To have a better grasp of the different factors that affect Diamond Cut quality, let’s take an in-depth look at proportions, primarily its table, width and depth. These features are widely measured and are superb barometers of a diamond’s cut quality.

Diamond Table Walkthrough

Diamond table % is calculated by dividing the width of the table (the top surface area) by the width (diameter) of the diamond. For example, if the table is 4.5 mm wide, and the diamond has a 6mm width, the table % is 75% (4.5/6 x100 = 75%).

When the table percentage is substantial, light will not be able to bounce off properly on the diamond’s crown angles and sides. Sparkling colors will not be visible, as the light will exit from the top surface of the diamond, eluding the eye.

When the table percentage is minimal, light will be confined inside the diamond and radiated through other parts of the diamond, escaping the eyes view.

The best table % relies strongly on the Diamond Shape. If you have any doubts about what makes up a superb table % for your diamond, we encourage you to contact us so we can guide you through the different options and factors.

Diamond Width Walkthrough

A diamond’s width is calculated by measuring its widest edge from end to end.

It becomes highly crucial when calculating the length to width ratio because it indicates how well balanced the diamond is along with its appropriate shape.

You can come up with your diamond’s length to width ratio by simply dividing its length by its width. Thus, if your diamond is 6mm long and 2mm wide, the length to width ratio is 3.

Diamond Depth Walkthrough

Depth % pertains to the how tall the diamond is, starting from its culet (the bottom tip of a diamond’s pavilion) towards the top of the table. With that being said, depth is calculated both in millimeters and percentage. You can come up with a diamond’s depth % by simply dividing its depth from its width.

So if your diamond has 5mm depth and 5.5mm width, for instance, its depth percentage would be 90.9% (5/5.5 x100 = 90.9%)

Most of the time, a lower depth % of two identical carat diamonds will come bigger because of the additional width. On the contrary, a very minimal depth % can bring a darker look, as it will not be able to reflect light effectively.


Diamond Cut and Diamond shape are two entirely different matters.

Diamond shape, like Pear Shaped and Round Brilliant, relates to the form and appearance of the diamond.

On the other hand, diamond Cut refers to the sides, angles, and reflective elements of the diamond. An Oval Shaped Diamond, for example, can have a shallow or deep cut and blunt or brilliant cut. It will still maintain the same shape but can follow a wide array of different cut styles. As a good rule of thumb, the more exceptional the cut, the more impressive its brilliance and fire will be and vice versa.


How effective a diamond will be in reflecting light and radiating brilliance will defend heavily on Diamond Cut Proportions. Diamond proportions pertain to the individual parameters comprising a diamond such as the angles to which it is cut and the specific length of different facets. A different mix of these parameters will affect how the diamond will interact with light, which is a great indicator of its overall beauty and timeless appeal (and also its GSI grading).

When a Diamond Cut is too shallow

If the cut on your diamond is too shallow, the light will reach the pavilion at a wide angle. As a result, the light will pass through the diamond and is emitted through the sides, instead of bouncing off from the table and towards your eyes.

Shallow cuts are often tempting options for ordinary or first-time buyers because of their apparent bigger size brought about by their wider table surface. This kind of cut, however, transmits light towards the bottom greatly decreasing the diamond’s brilliance, shine, and fire.

When a Diamond Cut is too deep

If the cut of your Diamond is too deep, on the other hand, light touches the pavilion at a sharper angle, which results in the light bouncing off to another pavilion. Light then retracts and travels though the bottom of the diamond. As a result, light is blurred and the diamond loses its vibrancy. Diamonds with deep cuts also create the illusion of smaller sizes compared to those that have ideal cuts.

The Best Diamond Cut

As a good rule of thumb, the ideal Diamond Cut is the one that provides optimum interaction with the light when it reaches each of its pavilions. With this kind of cut, the light doesn’t slip through the sides and other facets of the diamond but will bounce through the crown and table.

To label the highest grade, GIA utilizes the term “excellent” and AGS (the cut grade’s inventory) utilizes the term “ideal”. Both cuts possess perfect proportion of the best facet angles, bringing in a kind of brilliance and fire that travels through the table and towards the eye with great precision and quality.

With that being said, excellent cuts are more precious, radiant, and revered. If you have the money, the best route would be opting for a smaller, exceptionally cut diamond as opposed to a bigger carat with mediocre cut.

If you don’t know what kind of cut to follow for your diamond, don’t hesitate to ask for an expert’s opinion on the matter so he will guide you on the different essential factors that determine cut quality.


The GIA (Gemological Institute of America) is a popular and reputable name when it comes to grading diamonds.

Because it is an independent body, the opinions and reports of GIA are generally unfiltered and unbiased. If you are shopping for diamonds, it would be best to find a GIA certificate to evaluate the Diamond’s Cut grade.

Below is the scale in which GIA grades (as it claims) Diamond Cuts. Based on our experience, however, it’s sadly out of touch with the truth:


Diamonds that come with Excellent cut offer optimum level of fire and brilliance. Since majority of the light that it receives is bounced through the table, the diamond shines with amazing sparkle.

Very Good

Diamonds with Very Good Cut provide remarkable brilliance and fire. Most of the light that it receives is reflected in the diamond’s table. In plain view, these diamonds offer identical sparkle to those with an Excellent grade.


Diamonds that follow Good Cut grading display brilliance and shine, as much of the light it receives are bounced through the table towards the naked eye. Good Cut diamonds offer genuine beauty and appeal at lower price tags.


Diamonds that maintain Fair Cut grading provide minimal brilliance, since light tends to escape through the bottom and sides of the diamond. Fair Cut diamonds are solid options for smaller carats and those serving as auxiliaries.


Diamonds that are Poor Cut offer little to no sparkle, brilliance or fire. The light it receives instantly exits from the sides and the bottom of the diamond.

The truth is, more than half (55% to be exact) of all-round diamonds are given an excellent cut grade. Despite its superior grading, approximately 25-30% of these “excellent” diamonds are snubbed by our consultants when they are looking for diamonds primarily because of poor specs (depth, table and angles).

So that you don’t become an unlucky buyer of a lousy excellent cut, do contact us and we will let one of our consultants guide you through the entire process.


Since Diamond Cut plays a vital role in gauging the lasting appeal and brilliance of a diamond, here lies the twist.

So you will know exactly the Diamond Cut quality in a potential piece, consider these important factors:

  • Proportions: the ratios and sizes of the diamond’s depth, width and table
  • Symmetry: precision of the facets, mirrors, windows and steps
  • Polish: the shine and radiance of the diamond surface

If you are gauging the quality of a diamond cut, pay special attention to how its facets and angles reflect light. To be exact, try and see how bright and luminous the light reflection is when placed under a normal lamp.

You will need to determine the diamond’s fire (the rainbow light bouncing off) and its brilliance (the pure light and shine of the diamond). Also, make sure that you are taking special notice of the presence of dark spots within the stone.

If a diamond is badly cut (even if it possess excellent color or clarity grade), the majority of the light will not bounce back to your eyes, making it appears duller and lackluster.

Also, make sure that you are checking GIA’s cut grade on a diamond’s report, which will come with appropriate references as Poor, Good, Very Good or Excellent.


The accuracy and grade of a Diamond’s Cut, which can be summarized by its proportions and symmetry, will not only have a significant effect on its overall appeal but also its price.

When a diamond’s facets (its shiny surface levels) are proportional, for example, it will emit light to the naked eye powerfully. On the other hand, when it’s not excellently cut, its facets and pavilions will not emit light in the same fashion.

The quality of light and brilliance that especially cut diamonds provide are truly worth the additional price. Without brilliance and fire, a diamond won’t shine as bright — no matter the Carat weight or table size.

Putting more money on a diamond’s Cut instead of its Color or Clarity will have a tremendous effect on the overall beauty of your piece.

For instance, Brian Gavin offers a Signature collection known as Hearts & Arrows, which features some of the most exceptional Cut diamonds you can find on the market today. Its 1 Carat Diamond even maintains amazing brilliance at a superb price point.

If you want to limit your spending, we suggest skipping a GIA grade in Color and Clarity to guarantee that you are choosing the best-cut diamond for your money.


When you are on the market for the best diamond for your money, we highly recommend a quality Diamond Cut above anything else.  In terms of AGS Certified Diamonds, opt for an Ideal cut. If we are looking for diamonds, we always limit our choices on the quality of the Cut. You can learn more about our specification by checking out this James Allen Diamond search.

To enjoy optimum brilliance in your piece, think about a Brian Gavin Signature Cut. Brian is the top authority in the field of cut maximization. His diamonds are on the same level with the popular Hearts on Fire brand but with significantly lower price points.

When it comes to Round Brilliant Cut Diamonds, don’t put an ounce of faith to any online vendor’s cut grade. Restrict your attention to the GIA or AGS cut grade on the certificate.

Aside from evaluating GIA and other grading reports, don’t forget to personally examine the diamond yourself or let an expert do it for you. And most importantly, be sure that the diamond suites your personal taste and desires.

Our chief concern is to ensure that your diamond search is as seamless and efficient as possible and our mission is to help you land the best diamond for the money that you are willing to spend.

If you need our guidance on finding and selecting a diamond on the market, we will be more than glad to sort through the different cuts and make an unbiased recommendation for you.

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Kevin Lee is a former tech advisor who cut his teeth in Silicon Valley. He now spends his time sharing his passion for investing in diamonds and jewelry. You can reach Kevin for any comments by using this form.