Diamond Cut

When it comes to selecting a diamond, its cut is arguably the most critical factor in determining its overall beauty and brilliance. A diamond's cut doesn't refer to its shape (like round, oval, or pear) but rather how well the diamond has been shaped and polished from its rough state. 

What is Diamond Cut?

The cut of a diamond refers to how effectively it has been shaped and faceted. It's an artful balance of proportion, symmetry, and polish that greatly influences a diamond's ability to reflect and refract light. The cut determines how light enters the stone, travels within it, and then reflects back to the viewer's eye. This interplay of light is what makes a diamond sparkle and come to life.

The Impact of Cut on a Diamond's Appeal

The cut of a diamond profoundly impacts its overall appearance. Even a diamond with perfect colour and clarity can appear dull if poorly cut. On the other hand, a well-cut diamond with slight colour or inclusions can still display exceptional brilliance and beauty.

Diamond Cut Proportions

Diamond cut proportions refer to the relationship between different dimensions of a diamond. These proportions determine how well a diamond interacts with light, influencing its brilliance, fire (the dispersion of light into the colours of the spectrum), and scintillation (the sparkle or play of light as the diamond, the light, or the observer moves). 


Ideal / Excellent Cut Diamond

An Ideal / Excellent Cut Diamond represents the pinnacle of diamond cutting for maximising brilliance, fire, and scintillation. These diamonds are cut to exacting proportions and angles to ensure the most efficient use of light.

  • Light Performance: An ideal cut diamond is masterfully crafted to ensure that light entering the stone is reflected from one facet to another and then dispersed through the top of the diamond. This precise cutting results in a superior balance of white light (often referred to as brilliance) and colourful flashes (known as fire).
  • Proportions: Typically, for round brilliant diamonds, an ideal cut will have a depth percentage of around 59% to 62.3% and a table percentage of about 53% to 58%. However, these percentages can slightly vary depending on the shape of the diamond.
  • Symmetry and Polish: Along with proportions, the symmetry and polish of ideal cut diamonds are also of high quality, contributing to their overall appearance and light performance.

Shallow Cut Diamond

A Shallow Cut Diamond is cut in a way where the depth of the diamond is too low compared to its diameter.

  • Light Escape: In shallow cut diamonds, light that enters the stone often escapes through the bottom or the sides rather than being reflected back through the top. This results in less brilliance and can make the diamond appear lifeless or dull.
  • Appearance: These diamonds may appear larger due to their increased width or diameter, but they lack the depth required to create an intense sparkle. Additionally, shallow cut diamonds can sometimes create a visual effect known as a "fish-eye," where the viewer can see a dark circle in the centre of the diamond.
  • Depth Percentage: For a round brilliant diamond, a shallow cut would typically have a depth percentage lower than 59%.

Deep Cut Diamond

A Deep Cut Diamond has a greater depth relative to its diameter.

  • Light Leakage: In deep cut diamonds, light tends to leak out from the sides of the diamond rather than being reflected back through the top. This results in a loss of brilliance and makes the diamond appear darker and less lively.
  • Visual Size: Deep cut diamonds often look smaller than they actually are, due to their reduced width or diameter compared to their depth.
  • Depth Percentage: For round brilliant diamonds, a deep cut would have a depth percentage higher than 62.5%.

Grading the Cut: From Ideal / Excellent to Poor

A diamond's cutting grade is a critical evaluation that reflects how well a diamond has been cut and shaped from its rough form. This grade assesses the diamond's proportions, symmetry, and polish, which collectively influence its overall appearance, sparkle, and brilliance. The cutting grade is paramount because even a diamond with high colour and clarity grades can appear dull and lifeless if poorly cut. Conversely, a well-cut diamond can exhibit exceptional brilliance and fire, making it appear more beautiful and vibrant.

Ideal / Excellent Cut

  • Brilliance at its Best: An ideal / excellent cut diamond reflects almost all light that enters it, resulting in superior brilliance and fire.
  • Depth and Table: These diamonds fall within the ideal range for depth and table percentages.
  • Light Performance: Excellent symmetry and polish to maximize light return.

Very Good Cut

  • High Brilliance: Very good cuts reflect most of the light, offering a high level of brilliance, just slightly less than excellent cuts.
  • Proportions: Slightly outside the ideal range for depth and table, but still providing great light reflection.

Good Cut

  • Balanced Beauty and Value: Good cut diamonds offer a balance between quality and cost, reflecting a reasonable amount of light.
  • Variation in Proportions: More variation in depth and table percentages, but still a quality cut.

Fair Cut

  • Compromised Brilliance: Fair cut diamonds allow light to escape from sides or bottom, reducing brilliance and fire.
  • Proportions: Often too deep or too shallow, which allows light to escape easily.

Poor Cut

  • Lacking Brilliance: Poor cuts have noticeable issues in proportion and finish, resulting in minimal sparkle.
  • Significant Light Loss: These diamonds typically have extreme depth or table percentages, leading to significant light leakage.

Diamond Cut Depth Percentage

The depth percentage of a diamond is a measurement of how deep the diamond is in relation to its width. It's calculated by dividing the depth of the diamond (from the table to the culet) by its average diameter. This percentage plays a pivotal role in defining the stone's brilliance and fire.

Ideal Depth Percentage: For round brilliant diamonds, an ideal depth percentage typically ranges between 59% and 62.3%. However, this can vary slightly based on the diamond's shape.

Diamond Cut Table Percentage

The table percentage of a diamond refers to the size of the table (the flat top facet) relative to the width of the diamond. It is calculated by dividing the diameter of the table by the average diameter of the diamond.

Ideal Table Percentage: For most round brilliants, the ideal table percentage is usually between 53% and 58%.


If you would like any advice or guidance, contact us and we can guide you through the selection process and help you find the perfect diamond.