Diamond anatomy refers to the named parts, polished facets, measurements and angles used to describe a diamond’s physical structure. The principal parts of a polished diamond are the table, crown, girdle, pavilion and culet. Measurements such as table percentage, total depth, crown angle and pavilion angle explain how these parts relate to one another.
Understanding diamond anatomy makes it easier to read a grading report, compare diamonds and recognise why two stones with similar carat weights can look different. These structural details can influence face-up size, light performance, setting security and durability.
Diamond anatomy at a glance
| Diamond part | Where it is located | What it describes |
| Table | Flat facet at the top | Usually the largest facet of a polished diamond |
| Crown | Between the table and girdle | The upper part visible above the setting |
| Girdle | Around the widest perimeter | The boundary between the crown and pavilion |
| Pavilion | Below the girdle | The lower portion that extends towards the culet |
| Culet | At the bottom of the pavilion | The point or optional small facet at the base |
| Total depth | From the table to the culet | The diamond’s complete vertical measurement |
Each part contributes to the diamond’s overall appearance, but no part should be evaluated in isolation. A diamond’s visual performance depends on how its facets, angles and proportions work together.
Image placement 1 — Labelled diamond anatomy diagram
Recommended image: A precise side-profile illustration of a polished round brilliant diamond labelling the table, crown, girdle, pavilion, culet, total depth, crown height and pavilion depth.
Suggested alt text: Diamond anatomy showing the table, crown, girdle, pavilion and culet
What are the main parts of a diamond?
Table
The table is the large, flat facet at the top of a polished diamond. In most cutting styles, it is the largest individual facet.
Light can enter and leave the diamond through the table, but a larger table does not automatically produce a brighter or better diamond. Table size must be considered together with crown height, crown angle, pavilion angle and the other proportions.
On a grading report, table size is normally expressed as a percentage rather than only as a millimetre measurement.
Crown
The crown is the upper portion of the diamond extending from the girdle to the table. It includes the table and the surrounding upper facets.
In a standard round brilliant, the crown contains star facets, bezel facets and upper-girdle facets. These facets help gather and disperse light, contributing to brightness, fire and the pattern of light and dark seen across the diamond.
The height and angle of the crown can affect the balance between white-light return and coloured flashes. A crown should therefore be assessed as part of the entire proportion system rather than judged by one preferred angle.
Girdle
The girdle forms the outer perimeter of the diamond at the point where the crown and pavilion meet. When viewed from above, it defines the diamond’s outline.
The girdle is also the area normally held by prongs, a bezel or another setting component. Its thickness can therefore affect durability and setting security.
A very thin area may be more vulnerable to damage during setting or wear. An extremely thick girdle may retain extra weight without adding the same amount of visible face-up size. However, the final assessment depends on the girdle’s location, consistency, condition and the diamond’s overall design.
A girdle may be faceted, polished or bruted. Some grading laboratories can also place a microscopic report-number inscription on this part of the diamond.
Pavilion
The pavilion is the lower portion of the diamond extending from the girdle towards the culet.
Its facets help redirect light through the diamond and back towards the viewer. If the pavilion is too shallow or too deep in relation to the remaining proportions, more light may escape through the side or bottom of the stone.
Pavilion angle and pavilion depth are consequently important measurements, particularly when assessing a round brilliant. They must still be interpreted alongside the crown, table and other facet relationships.
Culet
The culet is located at the lowest point of the pavilion. It may be a sharp point or a small polished facet parallel to the table.
On a grading report, a culet described as None usually means there is no visible culet facet and the pavilion facets meet at a point. It does not mean that part of the diamond is missing.
Historically, larger culets were used to help protect the bottom point from damage. In a modern brilliant-cut diamond, a large culet can sometimes appear as a visible opening or dark point when the stone is viewed face-up.
What are diamond facets?
Facets are the flat, polished surfaces arranged across a diamond. Each facet acts like a small window or mirror, allowing light to enter, reflect and leave the stone.
The shape, size, alignment and angle of the facets all influence the diamond’s appearance. Facets that are poorly aligned or uneven can disrupt the intended pattern of reflections, even when the diamond has the expected number of facets.
How many facets does a round brilliant diamond have?
A standard round brilliant has 57 or 58 facets. The difference depends on whether it has a separate culet facet.
| Facet group | Number of facets |
| Table | 1 |
| Star facets | 8 |
| Bezel or kite facets | 8 |
| Upper-girdle facets | 16 |
| Pavilion-main facets | 8 |
| Lower-girdle facets | 16 |
| Optional culet | 0 or 1 |
| Total | 57 or 58 |
The table and 32 surrounding crown facets create 33 facets on the upper portion. The pavilion contains 24 facets, plus an optional culet.
More facets do not automatically mean better quality. Additional facets can create a modified pattern, but their number alone does not determine brightness, fire, symmetry or craftsmanship.
Fancy shapes can use brilliant, step or mixed facet arrangements. Their facet counts and patterns may differ considerably from those of a standard round brilliant.
Image placement 2 — Round brilliant facet map
Recommended image: A two-part technical diagram showing the crown and pavilion facet arrangement of a standard round brilliant. Label the table, star, bezel, upper-girdle, pavilion-main, lower-girdle and culet facets.
Suggested alt text: Facet arrangement of a 57 or 58 facet round brilliant diamond
Diamond measurements and proportion percentages
A grading report commonly records a diamond’s dimensions in millimetres. A round diamond is normally shown using minimum diameter, maximum diameter and total depth. Fancy shapes are generally reported using length, width and depth.
Proportion percentages describe how particular measurements relate to the diamond’s width or average diameter. This makes it possible to compare diamonds of different physical sizes.
Average girdle diameter
A polished round diamond is rarely perfectly circular. Its diameter is therefore measured in more than one direction.
The average girdle diameter can be calculated as:
Average girdle diameter = (minimum diameter + maximum diameter) ÷ 2
This average measurement is used when calculating several round-brilliant proportion percentages.
Table percentage
For a round brilliant, table percentage compares the average width of the table with the average girdle diameter:
Table percentage = (average table size ÷ average girdle diameter) × 100
A table percentage should not be used as a stand-alone quality score. Its effect depends on its relationship with the crown and pavilion.
Total-depth percentage
Total depth is the vertical distance from the table to the culet. For a round brilliant, total-depth percentage is calculated as:
Total-depth percentage = (total depth ÷ average girdle diameter) × 100
A comparatively deep diamond may retain more weight below the girdle and appear smaller from above than another diamond of the same carat weight. A very shallow diamond may appear wider, but its proportions can affect light return and durability.
For fancy shapes, depth is commonly compared with the diamond’s width. Reporting conventions can vary according to the shape and grading laboratory.
Crown angle and crown height
Crown angle describes the angle formed between the main crown or bezel facets and the table plane. Crown height describes the vertical distance from the girdle to the table, normally expressed as a percentage.
Together with table size, these measurements influence the diamond’s upper profile and how light is dispersed.
Pavilion angle and pavilion depth
Pavilion angle measures the relationship between the pavilion-main facets and the table plane. Pavilion depth describes how far the pavilion extends below the girdle.
Small differences in pavilion angle can materially affect a round brilliant’s face-up appearance. A pavilion that is too shallow or too deep in relation to the crown may allow more light to escape rather than return towards the viewer.
Star length and lower-half length
Star length describes the relative length of the star facets surrounding the table. Lower-half length describes the length of the lower-girdle facets on the pavilion.
These measurements can influence the size, contrast and appearance of the facet pattern. They should be read together with the principal angles and percentages.
How anatomy affects light performance
A polished diamond’s sparkle is produced by the interaction between light and its facet arrangement. The three principal visual effects are brightness, fire and scintillation.
Brightness is the white light reflected from the diamond, both internally and externally.
Fire is the separation of white light into visible spectral colours.
Scintillation describes the flashes of light and the pattern of bright and dark areas seen when the diamond, observer or light source moves.
Table size, crown angle, pavilion angle, facet alignment, polish and symmetry can all influence these effects. A single measurement cannot reliably predict the entire visual result.
For example, a diamond can have a table percentage that appears desirable on paper but still show weak light return if its crown and pavilion do not work effectively together. Conversely, more than one combination of proportions can produce an attractive diamond.
There is therefore no single proportion number that guarantees perfect light performance.
Image placement 3 — Light return and diamond depth
Recommended image: A three-part educational diagram comparing a shallow diamond, a well-proportioned diamond and a deep diamond. Use arrows to show light escaping through the pavilion in the shallow and deep examples and returning through the crown in the balanced example.
Suggested alt text: How shallow, balanced and deep diamond proportions affect light return
How anatomy can affect apparent size and durability
Carat is a measurement of weight, not visible diameter. Two diamonds of the same carat weight can therefore appear different in size when viewed from above.
A deeper stone may carry more of its weight in the pavilion or girdle. A shallower stone may spread more of its weight across its diameter. Neither characteristic should be considered independently from light performance, outline and durability.
The girdle can also influence how safely the diamond can be set. Very thin areas may be more susceptible to chipping, particularly near pointed or exposed sections. An extremely thick girdle can add weight without contributing proportionally to face-up size.
Fancy shapes require additional attention around vulnerable points. Pear, marquise, princess and heart-shaped diamonds are often protected using setting designs that support their tips or corners.
Reading diamond anatomy on a grading report
A grading report may include a profile diagram showing the measurements and proportions of the polished diamond. Depending on the shape and the laboratory, this can include:
- Physical measurements in millimetres
- Table percentage
- Total-depth percentage
- Crown angle and crown height
- Pavilion angle and pavilion depth
- Star-facet length
- Lower-half length
- Girdle thickness and condition
- Culet size
- Polish and symmetry grades
- Overall cut grade where applicable
An overall cut grade should not be confused with the diamond’s shape. For example, round describes the outline, while brilliant describes the cutting style.
GIA assigns an overall cut grade from Excellent to Poor to eligible standard round brilliant diamonds in the D-to-Z colour range. A fancy-shaped diamond may not display the same overall cut grade on a GIA report. Its absence does not automatically mean that the diamond is poorly cut.
Polish and symmetry are reported separately because they describe different aspects of workmanship. Polish concerns the condition and smoothness of facet surfaces. Symmetry concerns the precision and alignment of the facets and outline.
Common mistakes when interpreting diamond anatomy
Confusing shape with cut quality
Round, oval, pear and emerald describe shapes or outlines. Cut quality concerns how effectively the diamond’s proportions, facet arrangement and craftsmanship work together.
Looking for one perfect percentage
A table or depth percentage cannot establish quality on its own. Proportions work as an interconnected system.
Assuming more facets create more brilliance
Additional facets change the reflection pattern, but more facets do not automatically improve light performance or craftsmanship.
Treating every shape like a round brilliant
Fancy shapes use different outlines and facet arrangements. Standards developed for round brilliants should not automatically be applied to an oval, emerald, cushion or pear-shaped diamond.
Ignoring face-up appearance
Measurements and reports provide essential information, but they do not replace viewing the diamond. Pattern, outline, transparency, bow-tie visibility and overall appeal should also be considered.
Assuming a grading report guarantees beauty
A report describes measurable and assessed characteristics. Personal appearance preferences and the complete visual experience still require observation.
Do natural and lab-grown diamonds have the same anatomy?
Yes. Once polished, natural and laboratory-grown diamonds use the same anatomical terminology. Both can have a table, crown, girdle, pavilion, culet and polished facet arrangement.
They can also be cut into the same shapes and cutting styles. A round brilliant laboratory-grown diamond can therefore have the same standard 57- or 58-facet arrangement as a round brilliant natural diamond.
Their difference concerns origin and formation, not the names of their polished parts. Diamond anatomy alone cannot determine whether a stone is natural or laboratory-grown. That identification requires appropriate gemmological testing, and the origin should be disclosed on the grading report.
Image placement 4 — Natural and laboratory-grown diamond anatomy
Recommended image: A side-by-side technical illustration of polished natural and laboratory-grown round brilliant diamonds with identical table, crown, girdle, pavilion and culet labels. Add a note explaining that polished anatomy does not identify origin.
Suggested alt text: Natural and lab-grown diamonds showing the same polished diamond anatomy
Diamond anatomy checklist
When reviewing a polished diamond, examine the complete relationship between its parts rather than focusing on one number:
- Confirm the diamond’s physical measurements
- Compare carat weight with its face-up dimensions
- Review table and total-depth percentages
- Check crown and pavilion information where reported
- Review girdle thickness and consistency
- Check the culet description
- Review polish and symmetry
- Note the overall cut grade where applicable
- Examine the facet pattern and outline
- View the diamond under more than one lighting condition
- Verify that the report corresponds to the diamond
These checks help translate technical measurements into a clearer understanding of appearance, craftsmanship and practical suitability.
Frequently asked questions
What are the five main parts of a diamond?
The five principal parts are the table, crown, girdle, pavilion and culet. Total depth describes the complete vertical distance from the table to the culet.
What is the largest facet on a diamond?
The table is normally the largest facet. It is the flat surface located at the top of the diamond.
How many facets does a round brilliant diamond have?
A standard round brilliant has 57 facets when the pavilion ends at a point or 58 facets when it includes a separate culet facet.
Does a diamond with more facets sparkle more?
Not necessarily. Sparkle depends on facet placement, proportions, symmetry, polish and how the entire arrangement interacts with light. Facet count alone is not a quality grade.
What does “culet: none” mean?
It generally means that there is no separate flat facet at the bottom and the pavilion facets meet at a point.
What is diamond-depth percentage?
For a round brilliant, total-depth percentage compares the table-to-culet depth with the average girdle diameter. It helps describe how the diamond’s weight is distributed vertically.
Does a larger table make a diamond look larger?
A larger table can change the face-up appearance, but it does not necessarily make the whole diamond look larger or improve its cut. Diameter, depth and the complete proportion combination also matter.
Why is girdle thickness important?
The girdle forms the diamond’s perimeter and is normally held by the setting. Very thin areas may be more vulnerable, while an extremely thick girdle can retain weight without adding equivalent visible size.
Do all diamond shapes have the same facets?
No. Round brilliants have a highly standardised facet arrangement, while fancy shapes can use brilliant, step or mixed cutting styles with different facet patterns and counts.
Can diamond anatomy reveal whether a diamond is natural?
No. Natural and laboratory-grown diamonds can have identical polished anatomy. Specialised testing and the grading report are required to determine and disclose origin.
What is the difference between diamond anatomy and proportions?
Anatomy identifies the diamond’s physical parts and facets. Proportions describe their measurements, angles and relationships.
Can proportions alone predict how a diamond will look?
Proportions provide important evidence, but they should be considered alongside symmetry, polish, facet pattern, cut assessment and direct observation.
Understanding the complete diamond
Diamond anatomy provides the vocabulary needed to understand a polished diamond. The table, crown, girdle, pavilion, culet and facets are not isolated features. They form an interconnected structure that influences appearance, light behaviour, face-up size and durability.
A grading report makes these characteristics easier to compare, but no single percentage or angle tells the complete story. The most informed assessment considers the measurements, facet relationships, craftsmanship and actual face-up appearance together.
