A culet is the small facet, or point, at the bottom of a diamond, directly beneath the pavilion. It is part of a diamond’s cut and can affect how the stone looks, particularly when viewed through the table from above.
When we evaluate lab grown diamonds or loose lab diamonds, we usually want a culet that is small or absent because a large culet can become visible as a dark or light opening in the center of the diamond. However, the ideal choice depends on the diamond’s shape, cut quality, proportions, and overall appearance.
Understanding what a culet means can help us read a diamond grading report more confidently and compare stones based on more than carat weight or price.
(Related: What Does Pavilion Mean?)
What Is a Culet on a Diamond?
The culet is located at the very bottom of a traditionally cut diamond. It sits where the pavilion facets meet or terminate near the bottom of the stone.
Think of a round brilliant diamond as having several main areas:
- The table is the large flat facet at the top.
- The crown is the upper section between the table and girdle.
- The girdle is the narrow outer edge around the diamond.
- The pavilion is the lower section beneath the girdle.
- The culet is located at the bottom of the pavilion.
The culet is therefore quite different from the girdle or pavilion. If you are still learning diamond anatomy, our guides to what does pavilion mean, what does girdle mean, and what are diamond measurements can provide useful context.
What Does Culet Mean on a Diamond Grading Report?
When a diamond is professionally graded, its culet may be described using a scale such as:
- None
- Very Small
- Small
- Medium
- Slightly Large
- Large
- Very Large
The exact terminology can vary depending on the grading laboratory and report format.
A None culet does not necessarily mean the bottom of the diamond is perfectly sharp. Instead, it generally means there is no distinct culet facet visible at the bottom.
A Very Small or Small culet can also be perfectly acceptable. In many well-cut diamonds, it will have little or no noticeable effect on the appearance.
As the culet becomes larger, however, it may become more apparent when looking at the diamond from above.
Does the Culet Affect Diamond Sparkle?
Yes, the culet can influence the way a diamond interacts with light, although it should not be evaluated in isolation.
A diamond’s appearance is determined by a combination of factors, including its proportions, facet arrangement, symmetry, polish, depth, table, crown angle, pavilion angle, and cut quality.
A very large culet can potentially allow light to pass through the bottom of the diamond rather than being returned toward the viewer. Depending on the diamond’s overall proportions, this can reduce visual brightness or create a noticeable opening in the center.
For that reason, when we compare otherwise similar loose lab diamonds, a smaller or nonexistent culet is often a sensible preference.
That does not mean every diamond with a culet larger than "small" is automatically poor. The entire cut needs to be considered.
Is a Culet the Same as the Bottom Point of a Diamond?
Not exactly.
A diamond can have a pointed pavilion termination without having a separate culet facet. When a distinct small facet is polished at the bottom, that facet is called the culet.
This distinction matters because modern brilliant cuts can be designed with no visible culet facet. A grading report may therefore list the culet as "None."
The term is easier to understand when we remember that the culet describes a specific feature of the diamond’s pavilion termination rather than simply meaning "the bottom of the diamond."
(Related: What Does Crown Angle Mean?)
What Is the Best Culet Size for a Diamond?
For many buyers, None, Very Small, or Small is a good starting point.
A small culet generally provides the appearance we expect from a well-proportioned brilliant-cut diamond without creating an obvious opening in the center.
Here is a simple way to think about culet sizes:
| Culet | General buying consideration |
|---|---|
| None | Usually an excellent choice |
| Very Small | Generally a safe choice |
| Small | Usually acceptable and often difficult to notice |
| Medium | Worth examining carefully |
| Slightly Large | Compare visually before buying |
| Large | Can become noticeable |
| Very Large | May have a more obvious effect on appearance |
This is a guideline rather than an absolute grading rule. Shape matters, and so does the rest of the diamond’s cut.
Does Culet Size Matter for Lab Grown Diamonds?
Yes. The fact that a diamond is lab grown does not change the basic meaning of the culet.
Lab grown diamonds have the same fundamental crystal structure and optical properties as natural diamonds. Their cut characteristics, including culet size, are evaluated in much the same way.
When shopping for loose lab diamonds, we should therefore pay attention to the culet just as we would with a natural diamond.
The advantage of shopping online is that we can compare multiple certified stones side by side. Instead of selecting the first diamond that matches a particular carat weight and color grade, we can examine the complete grading information and look for the strongest combination of cut quality and visual performance.
How Does Culet Size Affect Different Diamond Shapes?
Culet considerations can vary considerably between diamond shapes.
Round Brilliant Diamonds
The culet can be particularly easy to evaluate in round brilliant diamonds because the symmetrical facet pattern makes the center of the stone visually important.
For a high-quality round brilliant, we would generally favor None, Very Small, or Small when all other factors are comparable.
Oval Diamonds
Oval diamonds can have different visual characteristics because their elongated shape and facet patterns vary significantly.
A small culet is generally desirable, but we should also inspect the diamond for bow-tie effects and evaluate its overall light performance.
For more guidance, see our article on the best ratio for an oval diamond.
Emerald Cut Diamonds
Emerald cuts are step-cut diamonds with large, open facets. Because these facets create broad reflections rather than the intense scintillation of a brilliant cut, clarity and proportions become particularly important.
A noticeable culet may be more apparent depending on the stone’s proportions and transparency. We should evaluate the entire face-up appearance rather than relying on the culet grade alone.
Our guide to the best ratio for an emerald cut diamond explains another important proportion to consider.
Pear and Marquise Diamonds
For pear and marquise shapes, the culet is only one part of the evaluation. Shape outline, symmetry, length-to-width ratio, and light performance can have a major effect on the diamond’s appearance.
If you are comparing elongated shapes, understanding length-to-width ratio can be just as important as understanding the culet.
Can a Large Culet Be a Problem?
A large culet is not automatically a problem, but it deserves closer attention.
The main concern is visibility. A large culet can sometimes appear as a distinct feature in the center of the diamond when viewed from above. In some cases, it can contribute to a darker or less lively central appearance.
This is why we would not recommend choosing a diamond based solely on its carat weight, color, and clarity grades.
For example, imagine two lab grown diamonds with similar:
- Carat weight
- Color
- Clarity
- Price
If one has a very small culet and the other has a noticeably larger culet, we would want to compare their actual appearance before deciding that they offer equal value.
The lower-priced diamond is not necessarily the better deal if its cut characteristics produce a less attractive appearance.
How to Check the Culet When Buying Loose Lab Diamonds
When comparing loose lab diamonds, we recommend using a structured approach.
1. Check the grading report
Look at the culet information on the diamond’s certification or grading report. This gives us an objective starting point.
2. Evaluate the complete cut
Do not judge the diamond by culet size alone. Check the available information about proportions, symmetry, polish, and other cut characteristics.
3. View the diamond from above
A grading report tells us important technical information, but the diamond’s actual appearance remains critical.
If high-resolution photography or video is available, inspect the center of the diamond for any obvious opening or unusual dark area.
4. Compare similar diamonds
The best way to understand value is to compare diamonds with similar carat, color, clarity, and shape characteristics.
This can reveal whether a lower price reflects a genuine value opportunity or a compromise in cut quality.
5. Ask for expert guidance when needed
If two certified diamonds appear similar on paper but have different culet sizes or proportions, expert guidance can help us determine which one offers the stronger combination of appearance and price.
Should We Avoid a Diamond With a Culet?
We generally should not reject a diamond simply because it has a culet.
In fact, many diamonds have some form of pavilion termination that is described as a culet. The important question is how large it is and whether it affects the diamond’s appearance.
For most buyers looking for a classic brilliant-cut appearance, None, Very Small, or Small is a straightforward preference.
A medium or larger culet deserves additional scrutiny, particularly when buying a loose diamond sight unseen.
Culet vs. Other Diamond Cut Features
It is useful to understand how the culet relates to other technical diamond terms.
The crown angle describes the angle formed by the crown facets and has a major role in the diamond’s interaction with light. Our guide to what does crown angle mean explains this measurement in greater detail.
The pavilion is the lower portion of the diamond beneath the girdle. The culet is found at its bottom termination.
The girdle forms the perimeter between the crown and pavilion.
The measurements describe the diamond’s physical dimensions, including length, width, and depth.
Together, these characteristics give us a much more complete picture than any single specification.
What Culet Should We Choose When Comparing Lab Diamonds?
For buyers who want a practical rule, we would usually prioritize None, Very Small, or Small culets, especially for round brilliant and other brilliant-cut shapes.
However, we should not pay a significant premium solely to move from a Small culet to None if the difference is invisible to the eye and the rest of the diamonds are comparable.
This is where smart comparison matters.
Suppose one certified lab diamond has a None culet but costs substantially more than a visually comparable stone with a Very Small culet. The second diamond may provide better value because the small difference in the report does not necessarily translate into a noticeable difference in appearance.
On the other hand, if a diamond has a large culet and a lower price, we should examine it carefully before treating the discount as a bargain.
Final Thoughts on What Culet Means
So, what does culet mean? It refers to the small facet or termination at the bottom of a diamond’s pavilion. The culet is a relatively small part of the diamond, but its size can influence the stone’s appearance when it becomes large enough to be visible through the table.
For most buyers comparing certified lab grown diamonds, None, Very Small, or Small is a sensible range to consider. Still, we should evaluate the culet alongside the diamond’s proportions, symmetry, polish, shape, and overall visual performance.
When comparing loose lab diamonds, the best value is rarely determined by one specification. A careful comparison of certified diamonds helps us identify a stone that combines attractive appearance, reliable grading information, and a price that makes sense for its overall quality.