Diamond Cut Grades Explained: Ideal, Excellent, 3EX and Hearts and Arrows
Updated: Oct 16
When shopping for a diamond, you will often encounter Ideal, Excellent, 3EX and Hearts and Arrows together. All suggest a well-cut stone, but they describe different things. Some are terms on a laboratory report, some describe a combination of three grades, and others refer to a particular pattern of optical symmetry. Understanding these distinctions helps you identify what makes a diamond's cut good.
Cut grade is an important starting point. Diamonds within the same grade can still have different proportions, contrast patterns and sparkling characteristics. RAGAZZA recommends identifying the reporting system first, then comparing proportion combinations and appearance. These layers of information also matter when choosing a high-quality lab-grown diamond.
Contents
1 What does a diamond cut grade assess?
Cut assesses a polished diamond's design and craftsmanship, and how these conditions affect its interaction with light. Round, oval and emerald describe shapes or cutting styles. Even diamonds with the same round brilliant cutting style can receive different cut grades.
A diamond's brightness, coloured flashes and sparkle in motion depend on how light enters, reflects between facets and returns to the observer. An appealing appearance needs both sufficient light return and a balanced pattern of light and dark. A diamond with no dark areas is not the complete objective of good cutting.[1]
Proportions, polish and symmetry
Component | What it assesses | What it means for a buyer |
|---|---|---|
Proportions | Geometry including table, total depth, crown and pavilion angles, and girdle | The structural basis for light paths and face-up size |
Polish | Facet surface finish and polishing features | Surface craftsmanship, which proportion measurements cannot replace |
Symmetry | Precision of outline, facet placement, size and arrangement | Consistency of cutting; it does not by itself verify Hearts and Arrows |
The overall cut grade is not a simple average of three fields. Laboratories use their own methods, and problems caused by proportions cannot simply be cancelled out by high grades elsewhere. Knowing the positions of the table, crown, girdle and pavilion makes a report's proportion diagram easier to read.
2 How laboratories determine cut grades
From optical measurement to craftsmanship assessment
Laboratories measure the polished diamond's dimensions, proportions and facet angles, and examine its polish and symmetry. IGI explains that an optical scanner creates a three-dimensional model of the polished stone's geometry. GIA also uses optical equipment to obtain proportion and angle measurements. These measurements, together with gemmologists' examinations, provide the basis for cut grading.[2][3]
The proportion diagram printed on a report summarises key information; it does not show the entire grading process. One table percentage, or a pavilion angle that falls within a particular interval, is usually insufficient to reconstruct the laboratory's overall assessment.
GIA's five round brilliant cut grades
For standard round brilliant diamonds in the D-to-Z colour range, GIA uses five cut grades: Excellent, Very Good, Good, Fair and Poor. Its assessment covers seven components, which can be understood through three areas.[1]
Area | Components | Main question |
|---|---|---|
Face-up optical appearance | Brightness, fire and scintillation | How do white light, coloured flashes and light-dark patterns work together? |
Design | Weight ratio and durability | Is excessive weight hidden in depth or girdle thickness, and does the design create damage risks? |
Craftsmanship | Polish and symmetry | How precisely are the facet surfaces and arrangement finished? |
Weaker components can limit GIA's overall cut grade; it is not an averaging system. However, a round brilliant with Very Good polish or symmetry can still receive an Excellent overall cut grade. Excellent in the Cut field therefore does not automatically mean that the other two fields are Excellent too.[4]
The focus of IGI's round brilliant grading
IGI evaluates round brilliants for proportions, polish and symmetry. Its official grading-process explanation calls the highest round brilliant cut grade Excellent-Ideal. Overall measurements and angles form the basis of the assessment, while lower finish grades may reduce the overall grade. This is a specific grading system: a retailer's description of a stone as an ideal cut is not sufficient evidence that it meets that system.[3]
3 Official proportion references for Ideal and Excellent
Identify whose Ideal grade you are reading
Ideal may refer to a description on an IGI report or in its associated data, or to a brand's own product label. GIA's regular five-grade round brilliant cut system has Excellent at the top; it does not add another grade called Ideal above it.[1][3]
The names alone therefore do not establish that every IGI Ideal diamond must outperform every GIA Excellent diamond. Meaningful comparisons still depend on the individual stone's proportions, craftsmanship and appearance. The names used by different laboratories do not form a universal ranking.
Specific conditions in IGI's official chart
The Cut-Grade Chart May 2023 currently linked from IGI's website includes the comment “Ideal Cut Round Brilliant” in its central Excellent column and sets out proportion ranges. The following selection shows several principal conditions behind this description.[5]
Parameter | Central Excellent column with the Ideal comment |
|---|---|
Total depth | 58.5%-62.5% |
Table | 53%-60% |
Crown angle | 33°-36° |
Pavilion angle | 40.0°-41.3° |
Polish and symmetry | Both at least Very Good |
The chart also includes crown height, pavilion depth, girdle requirements and other limitations. This is a selection, not a complete checklist for assigning Ideal yourself. Angles must also be considered together: selecting arbitrary combinations of upper and lower limits does not produce identical optical results.
The minimum finish requirements in this chart do not demand Excellent in both fields. Read the actual report field by field, preserving its original terminology. Ideal alone should not be taken as proof that polish and symmetry are both at the highest grade. The chart also has a version date; the formal report issued for the individual stone remains the reference for its laboratory result.[5]
GIA's published proportion ranges for Excellent
GIA also publishes proportion references. Parameter tables in its Estimating a Cut Grade booklet identify individual ranges within which Excellent remains a possible result. The following principal values come from the December 2009 revision. They help explain grading conditions, rather than providing a stand-alone guarantee of Excellent.[11]
Parameter | Reference range within which GIA Excellent remains possible |
|---|---|
Total depth | 57.5%-63.0% |
Table | 52%-62% |
Crown angle | 31.5°-36.5° |
Pavilion angle | 40.6°-41.8° |
Polish and symmetry | Excellent or Very Good in each field can still allow an Excellent overall cut grade |
GIA labels these ranges as allowing grades from Excellent to Poor. A value within a range can therefore still accompany a lower grade because of other conditions or the interaction between proportions. The crown-height and total-depth limits also apply to values derived from rounded key proportions. A single printed depth percentage should not be used as the entire grading decision.[11]
These interactions can change the result. One example in GIA's estimation tables keeps the other conditions constant but increases star facet length from 55% to 60%; the estimated cut grade changes from Excellent to Very Good. Minor facets can matter alongside the table, crown angle and pavilion angle.[12]
When comparing GIA and IGI, consider how each defines its parameters, treats proportion combinations and reaches the overall grade. A narrower range for one parameter does not establish that every top-grade stone from that laboratory is better.
Good cutting involves trade-offs
A cutter balances finished weight, face-up diameter, angle combinations, girdle thickness and facet finish. Retaining more weight does not necessarily make a diamond look larger. Weight hidden in a thick girdle or deep pavilion may increase the carat weight being purchased without a corresponding increase in face-up size.[4]
For a closer explanation of these measurements, read our Diamond Table and Depth Percentage Guide. Treat proportions as connected conditions rather than a set of independent passing numbers.
4 Comparing Excellent, Ideal, 3EX and Hearts and Arrows
3EX, also called Triple Excellent or Triple X, is a trade term for Excellent grades in Cut, Polish and Symmetry. It is not a sixth cut grade above Excellent, or a separate quality certificate.[6]
Term | What it describes | What it does not establish on its own |
|---|---|---|
GIA Excellent | The highest overall grade in GIA's five-grade round brilliant cut system | Excellent in all three fields, or identical appearance across every stone in the grade |
IGI Ideal or Excellent-Ideal | A round brilliant cut description that must be read within IGI's reporting system | Superiority over every top-grade diamond assessed by another laboratory |
3EX | Excellent in Cut, Polish and Symmetry | Verified Hearts and Arrows, or a separate light-performance assessment |
Hearts and Arrows | A pattern of optical symmetry visible under specific viewing conditions | The best possible proportions or strongest overall light performance |
Brand terms such as Super Ideal | Additional selection criteria set by a retailer or brand | A single threshold shared by all brands |
Hearts and Arrows images can help assess a round brilliant's optical symmetry, but the actual images, viewing conditions and pattern completeness matter. To learn how to read them, see our Complete Guide to Hearts and Arrows Diamonds.
A light-performance report is a more specific analysis service. IGI, for example, offers a separate Light Performance Report for round brilliants, with an overall score and component scores for brightness, fire and contrast. An ordinary IGI grading report should not be assumed to include that service. Its scope also matters: IGI states that its proportion-based light-performance analysis does not account for reduced transparency caused by dense clarity characteristics.[7]
AGS 0 or Ideal on older reports must likewise be interpreted within that reporting system. AGS Laboratories stopped providing services at the end of 2022, with its research and technology integrated into GIA. GIA's present AGS Ideal supplemental report is a separate service from an Excellent field on a regular report.[8]
5 Why diamonds with the same cut grade can differ
One grade includes many proportion combinations
Cut grading organises continuously varying geometry and optical conditions into a small number of categories. Two top-grade diamonds need not have identical crown angles, pavilion angles, table sizes, facet lengths or face-up contrast patterns. GIA explicitly explains that each grade includes a range of proportion combinations and face-up appearances.[1]
Two round brilliants with the same table percentage can still have different crown and pavilion angles. Even when key reported numbers are similar, the consistency and finish of individual facets leave room for comparison. Ranking stones by just one or two measurements can overlook these interactions.
A report does not replace viewing the diamond
Transparency and viewing conditions also affect how a diamond's interaction with light is seen. Spot lighting tends to emphasise coloured flashes, while diffuse lighting helps reveal overall brightness and patterns. Exposure, angle and background also change a photograph's appearance. Compare two diamonds under similar lighting and imaging conditions wherever possible.[7]
Two Ideal diamonds looking different does not automatically mean that one report is wrong. A more useful approach is to identify whether the difference comes from proportions, contrast style, transparency or photography, then decide which stone better fits your priorities.
How DAII supports a closer comparison
RAGAZZA's DAII™ Diamond Quality Index organises round-diamond quality information through 16 indicators, helping compare candidates with the same 4Cs and cut grade. It is RAGAZZA's selection-support model, not a laboratory cut grade. A difference in its scores should not be converted directly into a percentage difference in visible sparkle.
Read How the DAII™ Diamond Quality Index Works and Using DAII™ to Choose a Diamond for more detail. Data helps narrow a selection and explain differences; videos, images or the actual stone still matter in the final assessment.
6 Reading grades for natural, lab-grown and fancy-shaped diamonds
Natural and lab-grown diamonds follow the same optical principles
Natural and lab-grown diamonds are both diamond, so the optical principles relevant to cutting are the same. Lab-grown origin does not guarantee better proportions, nor does it mean a high-quality cut is inherently harder to achieve. Buyers need to check the finished cutting result and the reporting system being used.
Check the version of a GIA lab-grown report
From 1 October 2025, GIA changed its D-to-Z lab-grown diamond service to an overall Premium or Standard quality assessment. Premium requires D colour, VVS clarity or better, and Excellent polish and symmetry. Round brilliants must also meet Excellent cut requirements.[9]
Premium is therefore not a new, stand-alone cut grade. Standard should not simply be translated as average cut either: a stone may miss Premium because of colour or clarity rather than poor cutting. Earlier GIA lab-grown reports can still show the previous individual grades. Check the date and report type before interpreting the terminology.
For further comparisons, read GIA Premium Lab-Grown Diamonds Explained and Lab-Grown Diamond Certificates: GIA, IGI and NGTC.
Fancy shapes need a different approach
Oval, pear, emerald and other fancy shapes have different facet designs. GIA's regular diamond reports do not currently assign an overall cut grade to these shapes, although they assess polish and symmetry. The absence of a Cut Grade field is not evidence of poor cutting.[4]
IGI offers optional cut grading for fancy shapes, from Excellent to Poor. Its process combines polish and symmetry, proportion qualification, shape-specific craftsmanship requirements and a gemmologist's light-return assessment. It is therefore inaccurate to say that no fancy-shaped diamonds receive cut grades. One set of round brilliant table and depth limits should not be applied to every fancy shape either.[10]
7 How RAGAZZA selects cut quality worth buying
For high-quality lab-grown round brilliants, RAGAZZA recommends starting with high cut grades on reliable reports, then examining the finer differences. A top grade matters, but selecting a diamond should continue beyond finding Ideal or Excellent on the page.
A practical sequence from report to appearance
1. Check the report and stone details. Confirm the laboratory, date, natural or lab-grown origin, shape and report number. Read the original wording in Cut, Polish and Symmetry separately.
2. Compare proportion combinations. Consider the table, total depth, crown angle, pavilion angle and girdle together, and compare carat weight with face-up dimensions.
3. Examine craftsmanship and available images. For high-quality round brilliants, we prioritise Excellent polish and symmetry. Where Hearts and Arrows or light-performance data is available, analyse what it actually shows.
4. Watch a video or view the stone. Assess overall brightness, contrast patterns, movement and transparency rather than deciding from one photograph taken at its most sparkling angle.
5. Combine DAII with the budget comparison. For round diamonds, DAII helps organise candidates and compare the balance of quality and size at similar prices.
With a limited budget, we do not recommend sacrificing a clearly appealing face-up appearance simply to increase the printed carat weight. Nor should a more impressive product name alone justify a premium. Ask the seller which verifiable proportions, craftsmanship or optical characteristics explain the price difference.
Browse the RAGAZZA Diamond Inventory to compare reports, proportion data and available videos. You can also Arrange a Diamond Consultation for help comparing candidates. The aim is a stone with tangible quality reasons behind it that suits your budget and visual preferences.
8 Questions and answers about cut grades
Q1: Is Ideal always better than Excellent?
A: First identify the laboratory and reporting system. IGI's Ideal description and GIA's Excellent cannot be ranked by their names alone. Cross-laboratory comparisons should return to proportions, craftsmanship and appearance.
Q2: Does Ideal mean Excellent polish and symmetry?
A: Do not assume so. In the official chart linked from IGI's website discussed above, the central column permits a minimum of Very Good in both fields. Check each field on the actual report.[5]
Q3: Does 3EX guarantee Hearts and Arrows?
A: No. 3EX describes three grading fields. Hearts and Arrows requires optical images taken under particular viewing conditions. The two are related, but they are not the same finding.
Q4: Is Super Ideal a globally standardised certificate grade?
A: It is not a universal cross-laboratory grade. Ask a brand to explain its selection criteria and the reports or images supporting them.
Q5: Should I avoid a fancy-shaped diamond without an overall cut grade?
A: A missing field alone is insufficient to judge the stone. Identify the laboratory's service scope, then assess proportions, outline, light return and craftsmanship for that shape. Round brilliant Ideal criteria cannot be transferred directly.
Q6: Why do diamonds with the same top cut grade have different prices?
A: Cut grade does not encompass every factor affecting a diamond's value. Compare weight, dimensions, colour, clarity, proportions and appearance together to understand whether the price difference has a reasonable basis.
9 Sources
Prepared by RAGAZZA DIAMOND. Information checked on 16 October 2026. The following primary sources support the grading systems and technical explanations discussed above.
[1] GIA Diamond Cut — Round brilliant cut, optical components and proportion combinations
[2] GIA How GIA Grades Diamonds — Measurement, finish assessment and the grading process
[3] IGI Diamond Grading Process — Three-dimensional optical scanning and round and fancy cut assessment
[4] GIA Diamond Cut Grade 6 Things to Know — 3 February 2026: cut-grade limits, finish and fancy-shape scope
[5] IGI Cut Grade Chart May 2023 — Round brilliant chart linked from IGI’s official grading-process page
[6] GIA Triple X Diamonds — The definition of 3EX and the three grading fields
[7] IGI Diamond Cut Grading — Light-performance scores and transparency limitations
[8] GIA AGS Ideal Report — The current AGS Ideal supplemental report
[9] GIA Updated Laboratory Grown Diamond Services — Premium and Standard requirements introduced in October 2025
[10] IGI Fancy Shape Cut Grading — The four-stage fancy-shape grading method
[11] GIA Estimating a Cut Grade — December 2009 revision, pages 4–5: individual limits and proportion interactions
[12] GIA Cut Grade Estimation Tables — 2009, page 2: an example of star facet length changing the estimated grade
