How to Compare Two Certified Lab-Grown Diamonds

Start by making sure you are comparing the correct reports and the correct physical diamonds. Then compare them in this order: identity and report type, shape, carat weight, physical measurements, cut or proportions, colour, clarity, polish, symmetry, fluorescence and any relevant growth or treatment comments.

After that, separate what the documentation establishes from what you still need to judge visually. Do not assume that: the larger carat automatically looks larger; the higher colour automatically looks better; the higher clarity automatically looks cleaner to your eye; or the more impressive report automatically identifies the better purchase.

The question is not: Which report has the highest numbers? It is: Which diamond gives me the combination of verified specifications, visible appearance and purchasing value that I prefer?

Before comparing grades, identify the laboratory and report type. This matters because laboratory-grown diamond reporting is no longer uniform across all major laboratories.

IGI currently provides detailed Laboratory Grown Diamond Reports containing information such as description, shape, measurements, carat weight, colour, clarity and cut or finish information. GIA changed its principal colourless-to-near-colourless lab-grown service in October 2025. Eligible stones now receive an overall Premium or Standard Laboratory-Grown Diamond Quality Assessment rather than the previous natural-diamond-style colour and clarity nomenclature.

That means: IGI F / VS1 cannot simply be treated as the same type of result as: GIA Premium. The systems provide different kinds of information. Whenever possible, a direct comparison is easier when both diamonds have been evaluated under the same laboratory and report framework.

If the diamonds have IGI reports, first check the report numbers through IGI's official verification service. Then make sure the physical diamonds actually correspond with those reports.

A successful online lookup establishes that a report record exists. It does not automatically prove that the physical stone being offered is the diamond described by that report. Compare identifiers such as: shape; carat weight; measurements; reported grades; and the girdle inscription where one is present.

For the complete verification process, use How to Verify an IGI Certificate Number.

This distinction should remain central throughout the comparison.

That distinction prevents one of the biggest mistakes in online diamond comparison: turning assumptions into facts.

Consider two fictional IGI-reported round brilliant lab-grown diamonds. These values are examples only. They are not Aurelia inventory and do not represent actual products.

Diamond A: Carat Weight: 1.52 ct; Measurements: approximately 7.35 × 7.39 mm face-up diameter; Colour: F; Clarity: VS1; Cut: Ideal; Polish: Excellent; Symmetry: Excellent; Fluorescence: None.

Diamond B: Carat Weight: 1.48 ct; Measurements: approximately 7.31 × 7.34 mm face-up diameter; Colour: E; Clarity: VVS2; Cut: Ideal; Polish: Excellent; Symmetry: Excellent; Fluorescence: None.

At first glance, Diamond B seems to have stronger paper grades because it has higher colour and clarity. Diamond A, however, has slightly greater carat weight and slightly wider hypothetical face-up dimensions. Which is better? The report alone cannot answer that.

Based solely on the hypothetical reports, we can state that Diamond A is heavier. We can also state that Diamond A has slightly greater listed face-up measurements. Diamond B has the higher reported colour grade. Diamond B also has the higher reported clarity grade. Both carry the same hypothetical cut, polish and symmetry results.

Those are report-based comparisons. We should stop there before making visual claims.

We cannot say with certainty that Diamond A looks larger to every observer. We cannot say Diamond B obviously looks whiter. E is a higher colour grade than F, but the visible difference between adjacent high colour grades can be subtle, particularly when the stone is viewed individually.

We cannot say Diamond B looks cleaner. VVS2 is a higher clarity grade than VS1, but both may appear completely free of visible inclusions to an unaided observer depending on the particular stones. And we cannot say either diamond is more brilliant merely because of its colour or clarity grade. Those are the kinds of claims that require actual visual assessment or more detailed light-performance evidence.

Suppose Diamond B costs materially more because of its higher colour and clarity grades. If you cannot see a meaningful difference between E and F colour or between VVS2 and VS1 clarity, you may decide that Diamond A offers the more useful combination for you.

Another buyer may deliberately want E/VVS2 because high report specifications themselves matter to them. Neither decision is automatically wrong. The purpose of comparison is not to discover one universally superior grading combination. It is to determine which differences are meaningful to the particular buyer.

A fair technical comparison usually starts with diamonds of the same shape. Comparing a 1.50 ct round brilliant with a 1.50 ct oval can still be useful for choosing a style, but you are no longer making a straightforward quality comparison.

Different shapes distribute weight differently. Their facet patterns differ. Their length-to-width ratios differ. And their face-up dimensions can differ substantially at the same carat weight. If you are deciding between two ovals, compare two ovals. If you are deciding between two rounds, compare two rounds. Once shape is held reasonably constant, the other specifications become easier to interpret.

Carat measures weight. One metric carat equals 0.20 grams. If Diamond A is 1.52 ct and Diamond B is 1.48 ct, Diamond A is objectively heavier. What you cannot conclude from that alone is that Diamond A will look meaningfully larger. Visible dimensions depend on how the diamond's weight is distributed.

For this reason, carat and millimetre measurements should be compared together.

For the full principle, read Lab-Grown Diamond Carat Weight Explained.

Measurements help translate weight into physical scale. Two 1.50 ct round diamonds may have somewhat different diameters. Two 2.00 ct ovals may have noticeably different length and width combinations. This makes measurements especially useful when choosing between diamonds close in carat weight.

However, avoid another false conclusion: wider is not automatically better. A diamond can gain face-up spread by becoming too shallow or by distributing its proportions differently. Measurements therefore need to be interpreted alongside cut and proportions rather than treated as an independent quality score.

For carat versus visible dimensions, use Diamond Carat Weight vs Size.

For shapes where an applicable overall cut grade is available, cut deserves close attention because it relates strongly to how effectively the polished diamond handles light. Two diamonds with the same carat, colour and clarity can look very different if their cutting is different.

IGI says its round brilliant cut grading considers proportions together with research into brightness, fire, scintillation and pattern. IGI also currently offers a separate fancy-shape assessment framework combining finish, proportions, shape-specific requirements and light return. Do not simplify this to: higher cut grade = guaranteed prettier diamond. The grade is highly useful evidence, but individual visual preferences still matter.

For cut in depth, use Lab-Grown Diamond Cut Explained.

When comparing similar diamonds, proportions can help explain why two stones with similar headline grades may look different. For a round brilliant, useful measurements can include: table percentage; total depth; crown angle; pavilion angle; girdle; and culet. For fancy shapes, different proportions become relevant depending on the outline.

But this article should not create one universal "perfect proportions" table. Use proportions as supporting evidence rather than selecting a diamond through one ratio alone.

If two IGI diamonds are directly comparable and one is F while the other is G, F is objectively the higher colour grade. That does not automatically mean it is the better purchase. The more practical question is whether you can see or care about the difference in the intended setting.

Perceived warmth can be influenced by: diamond size; shape; lighting; viewing position; and surrounding metal. A buyer who values very high colour grades may choose the higher result. Another may accept a slightly lower grade because the visual difference is negligible to them.

For the full scale, use Lab-Grown Diamond Colour Grades Explained.

The same logic applies to clarity. If one IGI diamond is VVS1 and another is VS1, VVS1 is objectively the higher reported clarity grade. But that does not establish whether either stone contains an inclusion visible to your unaided eye.

IGI's current methodology considers the visibility, size, number, location and nature of clarity characteristics. The buyer-level question is: Does paying for the higher clarity grade produce a visible or personally meaningful benefit for me?

For clarity in depth, use Lab-Grown Diamond Clarity Grades Explained.

Eye-clean is a useful retail concept, but it is not the same thing as an official clarity grade. A VS2 diamond can potentially appear clean without magnification. Another similarly graded stone may have a more noticeable inclusion because of its location or contrast.

Stone size and shape also matter. Therefore: VS2 = eye-clean should not be presented as a universal equation. If eye-clean appearance matters, evaluate the actual diamond or reliable imagery rather than inferring the result mechanically from the grade.

Polish describes the quality of the diamond's facet surfaces after cutting and finishing. If both reports say Excellent polish, they are equivalent on that specific reported characteristic. Do not use: Excellent polish as though it meant: Excellent overall cut. They are separate report fields.

Symmetry concerns the alignment and precision of the diamond's shape and facets. Again, if two stones both receive Excellent symmetry, that field does not give you a reason to prefer one over the other. Move to characteristics where the stones actually differ. Comparison works best when it identifies meaningful differences, not when every matching specification is repeatedly discussed.

Fluorescence is another report characteristic that can be compared directly. But fluorescence strength should not automatically be translated into: good; bad; beautiful; or undesirable. Its visual effect depends on the diamond and viewing conditions.

If two otherwise similar stones differ materially in fluorescence and that characteristic matters to you, examine the actual stones rather than assuming the report label alone determines appearance.

IGI lab-grown reports can include comments relating to growth process and indications of post-growth treatment. If one report says: CVD growth process and another says: CVD growth process; indications of post-growth treatment those are genuine differences in manufacturing history.

But neither statement alone tells you which polished diamond is more attractive. CVD, HPHT and post-growth treatment should not be converted into automatic quality rankings.

For that topic, read CVD vs HPHT Lab-Grown Diamonds.

Where a report provides clarity-characteristic information, it can help explain why the diamond received its clarity grade. For two stones with the same VS2 grade, for example, the actual inclusions may be located differently. One might have a small characteristic closer to the edge. Another may have a more central characteristic.

This can affect how noticeable the inclusion is and, in some cases, whether its position deserves practical attention. Do not simply compare: VS2 vs VS2 = identical clarity. The grade is the same category. The stones themselves can still differ.

Girdle description can influence how a diamond carries weight and, in some circumstances, durability or setting considerations. A very thick girdle can retain additional weight that does little to increase face-up dimensions. Extremely thin vulnerable areas may deserve attention depending on the shape.

Do not choose a diamond solely from the girdle description, but include it as part of the complete proportion comparison.

Not every visually important characteristic appears as one simple report grade. For an oval, marquise or pear, buyers may care about the appearance of a bow-tie region. For an emerald or Asscher, buyers may focus strongly on step-pattern balance and how easily inclusions can be seen through the broad facets. For a cushion or radiant, facet pattern can make two stones of comparable grades look dramatically different.

These are visual observations. Do not imply that a report stating: Oval Brilliant, F, VS1 proves that the diamond has no visible bow tie. The report and actual visual evaluation answer different questions.

Once the reports have been compared, look at the stones in a comparable viewing environment if reliable imagery or in-person inspection is available. Ideally, compare them under the same: magnification; background; lighting; orientation; and image scale.

Otherwise the presentation itself can influence your judgement. A diamond photographed at a larger scale can appear more impressive even if its real-world dimensions are smaller.

Product imagery can show things that a report cannot. But it can also create differences that do not exist in the stones themselves. Exposure, white balance, contrast, background, camera angle and compression can all affect what you see.

For that reason, imagery should complement report data rather than override verified specifications. If a photograph appears inconsistent with the report, investigate rather than rewriting the grade from what the image seems to show.

Price should come late in the comparison. If Diamond A and Diamond B differ in: carat; colour; clarity; dimensions; cut; or another relevant characteristic, first understand those differences. Then ask whether the price difference makes sense for your preferences.

The higher-priced stone is not automatically better. The cheaper stone is not automatically better value either. Value depends on what you receive for the price and whether those differences matter to you.

A meaningful comparison holds as many variables constant as practical. Comparing: 1.50 ct round vs 1.51 ct round is far more useful for choosing quality than comparing: 1.50 ct round vs 2.00 ct oval.

Likewise, comparing two IGI-reported stones is easier than attempting to translate an IGI detailed report directly into GIA's current Premium/Standard lab-grown framework. The more variables that change simultaneously, the harder it becomes to know which difference actually influenced your preference.

This is a classic trade-off. Imagine one diamond is: 1.55 ct, G colour and another is: 1.45 ct, F colour. There is no universally correct winner. The first gives you additional carat weight. The second gives you the higher colour grade.

Now compare the actual millimetre dimensions. Then ask whether the colour difference is meaningful to you. The correct choice depends on which improvement creates more visible or personal value.

Do not automatically choose VVS. First determine whether both diamonds appear free of visible inclusions to you. If they do, the higher VVS result may primarily represent a microscopic grading advantage. Some buyers value that. Others would rather allocate the difference towards carat or cut. The report identifies the grade. The buyer decides how much that grade matters.

Then the report has done its job by telling you that many headline characteristics are comparable. Now look at the remaining differences. Measurements may vary. Proportions may vary. Inclusion location may vary. Facet pattern may vary. Shape appeal may vary. And the seller's price may vary.

Two diamonds with the same carat, colour, clarity and cut grade are not necessarily physically identical stones.

For current qualifying colourless-to-near-colourless GIA-assessed lab-grown diamonds, GIA's Premium classification requires the diamond to satisfy all applicable Premium criteria: VVS or higher clarity, D colour, Excellent polish and symmetry, and Excellent cut for round brilliants. Standard permits a defined combination down to VS clarity, E–J colour, Very Good polish, applicable symmetry thresholds and Very Good round-brilliant cut.

Because Premium and Standard are overall classifications, they should not be compared as though they were individual colour grades. A GIA Standard result does not tell you by itself whether the relevant Standard-level characteristic was colour, clarity, finish or a combination.

Only with care. Current IGI reports can provide detailed individual values such as: carat; colour; clarity; cut; polish; symmetry; and measurements. Current GIA qualifying D-to-Z lab-grown assessments instead classify the stone overall as Premium or Standard.

Therefore, do not create conversions such as: IGI E/VVS2 = GIA Premium or: IGI G/VS1 = GIA Standard. Those claims would overstate what the different systems establish. Keep each result attached to its own laboratory methodology.

Use the following worksheet when comparing two stones.

The final column is crucial. It prevents you from turning a personal impression into a laboratory fact—or treating a laboratory grade as though it automatically decides personal preference.

After completing the worksheet, ask three questions. First: Are there any factual disadvantages I care about? For example, materially smaller measurements, a lower cut result or a clarity characteristic in an undesirable position.

Second: Are the higher paper grades actually visible or meaningful to me? A one-grade improvement in colour or a jump from VS to VVS may matter greatly to one buyer and very little to another.

Third: Does the price difference reflect improvements I personally value? That is where comparison becomes a purchasing decision rather than a grading exercise.

No. Start with the differences. If both stones have: the same shape; same polish; same symmetry; same fluorescence; and comparable report type, those matching fields require little additional attention. Spend your time on characteristics that actually separate them. This makes the comparison faster and more useful.

Only if those specifications correspond with your priorities. A buyer who values very high technical grades may deliberately choose the stronger report. A buyer focused on visible size may prefer slightly lower colour or clarity in exchange for greater dimensions. A buyer focused strongly on light performance may prioritise cut and proportion characteristics over both. The report gives you evidence. It does not determine your priorities.

Start with facts. Confirm that both reports are genuine and correspond with the actual stones. Identify the laboratory and report type. Then compare: shape; carat weight; measurements; cut and proportions; colour; clarity; polish; symmetry; fluorescence; and any applicable growth or treatment information.

After that, stop treating every remaining question as something the report can answer. Does one look larger? Visual judgement. Is one eye-clean? Visual judgement. Does one oval have a more attractive outline? Visual judgement. Is paying more for E/VVS2 worthwhile compared with F/VS1? Purchasing judgement.

That separation is the key to comparing diamonds properly. A laboratory report establishes important facts. It does not decide which diamond you will prefer.

For understanding the grading process itself, continue with How Are Lab-Grown Diamonds Graded?

For the 4Cs framework, read What Are the 4Cs of Lab-Grown Diamonds?

For colour, use Lab-Grown Diamond Colour Grades Explained.

For clarity, read Lab-Grown Diamond Clarity Grades Explained.

For report interpretation, read How to Read a Lab-Grown Diamond Certificate.

For checking whether an IGI report corresponds with the diamond, continue with How to Verify an IGI Certificate Number.

When comparing Aurelia Royale diamonds, use the verified specifications and documentation for the specific stones being considered. Do not infer visual superiority from paper grades alone.

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