Grading Diamond Cut Scale

Grading the Diamond Cuts

Diamonds cuts is a measure of light performance as light hits a diamond. Diamonds sparkles as light hits a diamond, it bounces around and reflects within the diamond and ultimately exiting to your eye. Thus, is the sparkle that you see.
The cutting of a diamond directly impacts the amount of light performance achieved. The angles, locations, sizes and shapes of facets, all of these determine the diamond sparkle.

Before a diamond is cut and polished, it is known as a rough diamond. The rough diamond is opaque and often difficult to see through. Rough diamonds have little to no sparkle. This is because they lack facets or faces that bounce and reflect light.

The Cut Scale Of A Diamond

Diamond Cut Scale
Diamond Cut Scale-Kanjimull And Sons Jewelers

Fair & Poor Quality Diamonds

Diamonds with significant light leakage are Fair or Poor grade.
These diamonds leak noticeable amounts of light being too deep or shallow in height, thereby have little brilliance and are less visually appealing.

Fair or Poor cut diamonds do not meet With Clarity’s minimum light performance criteria. Avoid these diamonds as they will not make for sparkling jewelry.

Very Good

These diamonds are very brilliant with minimal light leakage. Diamonds cut of a Very Good grade can improve upon the other characteristics of the diamond such as Color, Clarity or Carat as well. The top 15% of gemstone quality diamonds are Very Good cut. Very Good cut diamonds can be a great choice if looking maximize value on the other factors.


Good cut diamonds have some light leakage, but overall shine bright. These diamonds can have noticeably larger or even smaller measurements than perfectly cut diamonds of the same shape. The top 25% of diamonds have a Good cut grade. Good cut diamonds can be a good blend of value and size, however always ask a gemologist to assess the particular diamond for you before you make a decision.


Diamonds with a top cutting design, grades are expertly crafted and precisely cut to deliver the maximum sparkle and brilliance of a diamond. Little or no light leakage occurs as light passes through a diamond. This premium category represents the top 3% of all diamonds. Excellent cut diamonds are increasing with improvements in manufacturing technology. An excellent cut diamond is always a good choice regardless of diamond shape and size.

Understanding Light Cut

Light Cut is made up of factors such as reflection, refraction, and dispersion. The better and more uniformly a diamond is able to reflect and showcase light, the better of a diamond it is as it will sparkle more in your jewelry.


Diamond Reflection

When a diamond is rocked and tilted at different angles, some light reflects on the surface of facets rather than bouncing around inside the diamond. This is known as reflection. Typically, about 17% of light is actually reflected by the diamond. Reflection should be balanced. When facets are too large, we can see reflections either strengthen or weaken too much, which will cause the diamond to seem dull.


Diamond Refraction
Diamond Refraction

The ideal diamond is cut such that light enters, bounces around, bends and ultimately exits from the top of the diamond. This concept is known as refraction. Diamonds score a 2.41 on the refractive index, which is high and gives diamonds their sparkly characteristics. With ideal cutting, the refraction is most noticeable. With a diamond that is cut well, light reflects perfectly within the diamond.


Diamond Dispersion
Diamond Dispersion

You can see all the colors of the rainbow reflecting from within the diamond. That’s a result of dispersion. As light bounces around in a diamond, bends and then exits back to your eye, a diamond’s dispersion is measured at 0.44. It is most commonly known as the fire within a diamond. The visibility of all these colors is what gives diamonds a unique beauty.

Other gemstones typically do not have the same beautiful dispersion that diamonds have. Therefore, diamonds are considered to be the most popular choice for engagement rings and jewelry.

Finish: Polish, Symmetry and Facets

Other factors that affect the cut grade are polish, symmetry and faceting. Diamonds are typically cut in two ways: step cuts and brilliant diamond cuts.

Diamond Step Cut
Step Cut

Step cuts, such as Emerald cut diamonds and Asscher cut diamonds, have sparkle or fire. They have facets that look like a staircase and are a bit simpler in presentation.

They are considered very elegant and maximize the diamond’s scintillation. These cuts are elegant but because they have fewer facets do not reflect light as much as brilliant cut diamonds. While both diamonds have unique beauty, it is important to consider which type of diamond sparkle you want while picking a diamond cut.

Brilliant Diamond Cut

Brilliant cuts, most commonly Round cut diamonds or Princess cut diamonds, have maximum diamond sparkle. They possess more facets than step cuts and the facets are triangular and kite-shaped. Brilliant cuts have a high degree of diamond sparkle and maximum the fire and scintillation of a diamond.

Moreover, polish and symmetry are a result of the manufacturing process.

The polish of a diamond is how cleanly smooth the facet surfaces are. If small striated polish lines remain, it may affect light performance and therefore, diamond cut.

The other attribute is symmetry. Symmetry is simply the pattern and evenness of the size, shape and location of facets. If the location of a facet is incorrect, the performance of light and therefore the cut grade can be affected. For example, an off center table facet may reduce diamond sparkle.

Selecting Cut Grade

Excellent cuts are most premium and Very Good cuts offer more value. The differences in sparkle are quite subtle, but they are noticeable when compared side by side. We recommend maximizing on the Cut grade, if possible. Fancy shapes have less restrictions because beauty is in the eye of the beholder. Still, you can often safely go a grade lower with non round diamond shapes. Excellent cut fancy shapes are fairly rare.

Try and maximize on the cut score and grade of the diamond. This represents the sparkle of the diamond and can help mask (or make up for) lower clarity grades, color tints, or smaller than desired carat weights. You may find value in a “Very Good” cut diamond that have most of the technical aspects of a Excellent cut diamond, but missed the cut off by a technicality such as a thick girdle or larger table facet.

In the end, it’s your decision and you must remember there are plenty of other factors that influence a diamond. You must choose which factors/attributes matter most to you.

Do check our post on How Are Diamonds Made

Still not sure which cut to choose? Feel free to contact us for personal help. Our experts are here to help you with the very best diamonds to choose from.

2 thoughts on “Grading the Diamond Cuts”

  1. Pingback: Kanjimull & Sons Jewellers - KANJIMULL & SONS JEWELLERS

  2. Pingback: Kanjimull & Sons Jewellers - KANJIMULL & SONS JEWELLERS

Leave a Reply


Scroll to Top
Open chat