How are lab-grown diamonds graded and certified?
Lab-grown diamond grading checks what the stone is and describes its characteristics. For a loose diamond or an engagement-ring center stone, we would want to see the actual laboratory report before buying. It helps you compare diamonds and check that the seller's description matches the stone.
The four Cs are the familiar starting point: cut, color, clarity and carat weight. But there is an important difference between current report formats. IGI continues to use individual four-Cs grades; GIA's newer D–Z lab-grown service uses an overall Premium or Standard assessment. Do not assume every report gives you the same information.
Our practical advice is to read the document, check its number with the issuing laboratory and inspect the actual diamond. A report helps narrow your choices; it does not replace deciding whether you like the stone.
| Check | Why it matters |
|---|---|
| Laboratory and report number | Lets you look up the document with its issuer |
| Laboratory-grown identification | Confirms the stated origin rather than leaving “diamond” ambiguous |
| Weight and measurements | Helps you match the report to the listing and compare visible size |
| Grades or assessment | Explains the reported quality using that laboratory's format |
| Cut, finish and proportions | Helps assess cutting quality, with different information for different shapes |
| Comments and inscription | May include treatment information and a number to match on the stone |
What are diamond certificates?
Shoppers and sellers often call a grading report a “diamond certificate.” The more useful question is what the document actually covers and who issued it.
A grading report describes a diamond's identity and characteristics. It is not automatically an appraisal, insurance valuation or guarantee of resale value. GIA, for example, explicitly calls its documents reports rather than certificates and does not state an appraisal value. GIA explains that distinction here.
Reports also vary in detail. Some include a clarity plot, photograph or extra cut analysis; others do not. A missing plot is not, by itself, a reason to dismiss a report.
For a substantial center stone, independent grading is something we value. For a piece with many tiny accent diamonds, you may instead receive specifications for the finished jewelry, without an individual report for every stone. Check whether the quoted grades describe the center diamond, all diamonds, or a range.
How are lab-grown diamonds graded?
A gemological laboratory first establishes the material and its origin, then measures and assesses the characteristics covered by its service. Instruments, controlled lighting, magnification and trained graders all play a role. Origin identification and quality grading answer different questions: a stone being laboratory-grown does not automatically make it high grade.
For shopping, the report is most useful when you connect each result to the diamond's appearance. Our four-Cs guide explains the buying priorities; the sections below explain what the grades mean.
Lab-diamond color grading
The D–Z scale describes the amount of tint in a diamond. D is the highest colorless grade; D–F are grouped as colorless and G–J as near-colorless. Grading uses controlled conditions rather than the lighting in a jewelry display.
A color grade does not tell you exactly how much tint you will notice once the stone is set. Shape, size, lighting and metal all affect that impression. We often compare F–H for a white-looking round, while including D–E when the extra cost is small. See our color guide for examples and buying advice.
Lab-diamond clarity grading
Clarity describes internal features called inclusions and surface features called blemishes. The familiar scale runs from Flawless (FL) through Internally Flawless (IF), VVS, VS and SI to Included grades I1–I3. Grading considers features under 10× magnification, including their size, position and visibility.
For buying, we care about whether marks or haziness distract from the stone. “Eye-clean” means inclusions are not visible to the unaided eye at a normal viewing distance; it is not a formal extra laboratory grade. VS1–VS2 can be a useful search starting point, but inspect the actual diamond rather than treating any grade as a guarantee. Our clarity guide explains the trade-offs.
Lab-diamond cut grading
Cut describes the cutter's work, including proportions and facet arrangement, rather than simply the diamond's outline. It affects brightness and the flashes you see as the stone moves.
For a round diamond, we would start with an Excellent or Ideal search filter and then read the laboratory's own result. Retailer labels are not always identical to laboratory terminology. IGI's current highest round cut grade is Excellent–Ideal, and it also offers cut grading for fancy shapes. IGI explains its round and fancy cut assessments.
We would generally protect cut quality before stretching for more weight. A high color or clarity grade does not make a dull-looking diamond sparkle. The cut guide goes through what we would check in videos and reports.
Lab-diamond carat grading
Carat is a measurement of weight, not a quality score. One carat equals 0.2 grams. A heavier diamond is not automatically better cut or more attractive.
Read the measurements in millimeters alongside the carat weight. Two diamonds of the same weight can look different in size because of their shape and depth. In multi-stone jewelry, distinguish the center stone's weight from total carat weight. Our carat guide explains these comparisons.
Grading fancy-shaped lab-grown diamonds
Fancy shapes are outlines other than round, including oval, pear, emerald, cushion and heart. They are not the same thing as fancy-colored diamonds.
The old blanket advice that fancy shapes never receive a cut grade is out of date. IGI's fancy cut assessment includes polish, symmetry, proportions, craftsmanship and light return. Still, read the particular report: not every document includes the same cut information.
Symmetry
Symmetry assesses aspects of how the shape and facets line up. It is useful information, but an Excellent symmetry grade alone does not establish excellent overall cut or guarantee a pattern you like.
For a heart or pear, look at the outline as well as the report. For an oval, inspect the center and ends as it turns. Personal preference still matters: a longer outline is not automatically better than a rounder one.
Polish
Polish describes the finish of the facets. Poor finishing can affect appearance, but the polish grade is only one part of evaluating a diamond. “Excellent polish and symmetry” should not be read as “Excellent cut” unless the report actually states an overall cut grade.
Proportions
Length, width, depth and table measurements help explain how a diamond is shaped. A deep stone may carry weight you do not see face-up. A pleasing outline can also vary between buyers and jewelry styles.
Do not force every fancy shape into one ideal-ratio rule. Proportions alone cannot fully describe light performance. Inspect the video and compare the pattern: an emerald cut's broad flashes should not be judged as if it were a round brilliant.
Grading fancy-colored lab-grown diamonds
Fancy-color grading considers the color itself, including hue, tone and saturation. It is a different assessment from the D–Z scale, not a “Z+” extension. Reports should also identify laboratory origin and relevant treatment information.
The descriptions below explain terms you may encounter. They are not a simple price ladder. The full color description and the actual diamond matter more than choosing the strongest-sounding word.
Faint
Faint describes very weak color within the applicable color-grading system. Do not assume a stone has a vivid face-up color because a listing mentions pink, blue or another hue.
Very Light
Very Light also describes a delicate color appearance. Compare the actual stone in realistic lighting if a soft tint is what you want.
Light
Light is another color-strength description. Check the complete report wording rather than translating it into a D–Z letter grade yourself.
Fancy Light
Fancy Light can suit someone who likes a softer-colored diamond. Whether it is appealing depends on the hue, the individual stone and the finished jewelry.
Fancy
Fancy is a specific grading term when used in a color description, not just a general word for decorative jewelry. Read it together with the named color and any modifying hue.
Fancy Intense, Fancy Vivid and other descriptions
Fancy Intense and Fancy Vivid describe stronger color appearances. Fancy Deep and Fancy Dark also occur in the system, reflecting different combinations of tone and saturation. They are not simply grades above Vivid. GIA explains how colored diamonds are assessed.
We would choose a fancy-colored diamond by the color you enjoy and its appearance in the setting, then compare prices for similar stones. The rarity and pricing of natural fancy colors should not be used as a shortcut for valuing a laboratory-grown stone.
Who grades lab-grown diamonds?
The laboratory name matters, but so does the service and date printed on the report. Here is how we would read the main names and older documents you may encounter.
Gemological Institute of America (GIA)
GIA is an independent nonprofit gemological organization. Its lab-grown service changed on October 1, 2025: for D–Z laboratory-grown diamonds, the newer assessment uses Premium or Standard based on combined criteria rather than listing the familiar individual color and clarity grades in the previous format. Stones below the minimum Standard criteria do not receive that assessment.
That means “GIA Standard” is not a single color or clarity grade. An older GIA report with individual grades is not automatically invalid because the service changed. Check the actual report and its date. GIA publishes the criteria and change here.
International Gemological Institute (IGI)
IGI continues to issue lab-grown diamond reports using individual four-Cs information. That makes them convenient when comparing a particular color and clarity combination across sellers. IGI confirmed that approach in its grading statement.
For most of our lab-grown diamond shopping, IGI is a practical starting point. We would still inspect the actual stone and read the report's cut and treatment information instead of buying solely on the highest headline grades.
American Gem Society Laboratories (AGS Laboratories)
AGS Laboratories is a name you may see on older reports. It closed in 2022, with its research team and intellectual property moving to GIA. AGS describes that transition.
An old AGS report should therefore be read as an existing report, not evidence that AGS Laboratories is still accepting stones as a separate grading service. The American Gem Society itself is a separate continuing organization.
Gem Certification & Assurance Lab (GCAL)
GCAL by Sarine is another grading option. It provides diamond reports and cut-related analysis; its certificate products may also include a grading guarantee under their stated terms. Sarine explains its report offerings.
Read the actual document and guarantee wording rather than treating “certified” as a promise covering every future problem, loss or change in value. Extra cut information can be useful when comparing appearance, but it does not remove the need to inspect the diamond.
European Gemological Laboratory (EGL)
If you encounter an EGL-labelled document, check the exact issuer, date and report details. We would not choose a diamond just because an unfamiliar report gives it a higher grade than another laboratory's stone.
Our preference for a new lab-grown purchase is a clearly verifiable independent report with enough information to compare the diamond confidently. If the paperwork is unclear, ask for independent assessment before committing.
Jeweler grading
A jeweler's in-house grade is not the same as a report issued by an independent laboratory. It can describe the seller's selection, but we would be clear about who assessed the stone.
For example, VRAI normally uses in-house grading and offers an optional IGI report for a fee and additional time. Our VRAI review explains that choice. Ask before ordering if independent grading is important to you.
A short history of diamond grading
Before standardized grading, buyers had a harder time comparing descriptions from different sellers. GIA developed the familiar international diamond grading system in 1953. The four Cs gave the trade and consumers a shared way to discuss weight and quality.
Laboratory-grown diamonds made origin identification another important part of that conversation. Today's report changes are a reminder to read the document rather than assume that a laboratory's name always means the same format.
Frequently asked questions
Do lab-grown diamonds get certified?
Yes, lab-grown diamonds can receive independent grading reports, commonly called certificates. Not every diamond in a finished piece has an individual report, especially tiny accent stones. Check what documentation comes with your specific purchase.
What are the grades of lab-grown diamonds?
Many reports use D–Z color, FL–I3 clarity, carat weight and applicable cut and finish grades. Current GIA D–Z lab-grown assessments instead use Premium or Standard. Read the laboratory and report format before comparing labels.
Which certification is best for a lab-grown diamond?
We generally start with an independent IGI report because its individual grades make lab-grown comparisons straightforward. GIA and GCAL documents can also be useful. The best report for your purchase is one you can check with its issuer and use to understand the actual diamond, not merely a reassuring logo.
Is GIA or IGI better for lab-grown diamond grading?
Both are established laboratories, but their current lab-grown formats differ. IGI retains individual four-Cs grades, while newer GIA D–Z assessments group qualifying diamonds as Premium or Standard. We find the individual grades useful for price comparisons; that preference does not mean a GIA-assessed diamond is a poor choice.
Our bottom line
A grading report is one of the most useful tools you have when buying a lab-grown diamond. Check origin, measurements and quality information, then compare the actual appearance and price. Do not confuse a high grade with a guarantee that the stone is the right one for you.
Where to buy lab-grown diamonds with grading reports
Choose a seller that makes the individual report available before purchase. Match the report number to the listing, and ask any questions while you can still change your choice. Keep the document with your purchase records.
Three jewelers we recommend comparing
Ritani is our usual starting point for loose-diamond value. Blue Nile is worth comparing for its established shopping experience, and Brilliant Earth for designs and shopping options you may prefer despite higher prices. Our jeweler comparison explains the differences.