What a grading report actually is
A diamond grading report is the lab's independent description of your diamond. It is not a sales document and it is not an appraisal of value. It is a neutral third party, a gemological laboratory with no stake in the sale, telling you what the stone is. To read one, look for five things: the lab name, the report number, the 4Cs (cut, color, clarity, carat), the measurements, and the shape line. Then confirm the report number on the lab's own website. That last step is the whole game, and you can do it yourself in under a minute.
We source Lab Grown Diamonds and hand-set them into rings in NYC, so we read these reports every day, on both sides of the counter. This is the jeweler's-bench version: what each line means, what the report can and cannot tell you, what the October 2025 GIA change did to Lab Grown grading, and how to verify a report is real. The point is not to make you suspicious. It is to put the verification power in your hands, because a buyer who can read the paper buys with a clear head.
The five lines to read first
A report can look dense, but the lines that matter sort into five groups. Read them in this order and you have read the report.
The lab name. At the top: GIA (Gemological Institute of America), IGI (International Gemological Institute), or GCAL. These are the independent labs whose paper means something. The name tells you whose standard graded the stone.
The report number. A unique number, usually near the lab name and often repeated as a tiny laser inscription on the diamond's girdle. This is the key you use to verify the report online.
The 4Cs. Cut, color, clarity, and carat weight. For a deeper read on what each one changes and where to spend, see our guide to the 4Cs. On a Lab Grown Diamond report, look for the "LG" prefix or a note that the stone is laboratory grown.
The measurements. The stone's dimensions in millimeters (length by width by depth), plus the table and depth percentages. This is how you judge the actual size and the proportions, and how you confirm an elongated shape's length-to-width ratio.
The shape line. Listed as "shape and cutting style." This describes the geometry in the lab's own vocabulary, which is not always the trade name a seller uses. More on that below.
Everything else on the page (fluorescence, polish, symmetry, the plotted inclusion diagram) is useful detail, but those five lines are the spine. If you can find and read them, you can read any report.
GIA vs IGI, and what changed in October 2025
GIA and IGI are both reputable, independent labs, and a stone from either is a verified stone. But for Lab Grown Diamonds, the two now describe quality differently, and this is the single most important change a 2026 buyer needs to understand.
In October 2025, GIA changed how it grades Lab Grown Diamonds. Instead of the familiar letter and number grades for color and clarity, GIA moved Lab Grown reports to two descriptive tiers, "Premium" and "Standard" (GIA, 2025). The practical consequence is that the report no longer prints a precise color and clarity grade on most Lab Grown stones. A stone that would have graded E VS1 and a stone that would have graded J VS2 can now carry the same "Premium" label, even though one is a noticeably finer stone. The descriptor flattens real differences you would otherwise pay for, or save on.
IGI did not make this change. IGI still issues a full 4Cs report for Lab Grown Diamonds, with the specific color grade, the specific clarity grade, and the carat weight spelled out (IGI, 2025). So if you want to know exactly what you are buying, an IGI report gives you more to read. This is not a knock on GIA, whose standards are excellent. It is simply that, for a Lab Grown stone in 2026, the IGI report carries more line-item detail than a GIA Premium or Standard descriptor does.
| For a Lab Grown Diamond | GIA (after Oct 2025) | IGI |
| Color grade | Folded into "Premium" or "Standard" | Specific letter grade (D to Z) |
| Clarity grade | Folded into "Premium" or "Standard" | Specific grade (FL to I) |
| Carat and measurements | Yes | Yes |
| Online verification | Yes | Yes |
GIA moved Lab Grown reports to "Premium" and "Standard" descriptors in October 2025; IGI continues to grade the full 4Cs (GIA and IGI, 2025). Always confirm the report on the issuing lab's own site.
How to verify a report is real
A report is only as good as the database behind it, and the good news is that both labs publish that database for free. Verifying a public grading report is a normal, welcome thing to do. A reputable seller wants you to confirm it, because it proves the stone is exactly what was described. Here is the whole process.
Read the number, then match it on the lab's site
Take the report number from the document and type it into the lab's own report-check page (GIA's Report Check, IGI's Verify Your Report). The lab's record should match the document in front of you, line for line: same carat weight, same measurements, same grades or descriptor, same shape. If the numbers match, the report is genuine. If the lab has no record of that number, or the details differ, stop there.
Check the girdle laser inscription
Most lab reports note a laser inscription, the report number etched microscopically into the diamond's girdle (the thin band around its widest point). Under magnification, the inscription on the stone should read the same number as the report and the online record. On a Lab Grown Diamond it typically carries an "LG" prefix. That single number, appearing in three places (the document, the lab's website, and the stone itself), is how a report ties to a specific physical diamond rather than to a stand-in.
That is the entire verification. It takes a minute, it costs nothing, and it is the most powerful tool a buyer has. You do not need to challenge anyone or demand anything to do it, the report number is public by design.
What the report does and does not tell you
A grading report describes a stone's measurable facts. It does not tell you whether the stone is beautiful, whether it suits the hand, or what it is worth in dollars. Those are judgments the report cannot make. A few specifics are worth knowing so the document does not surprise you.
It prints geometry, not trade names. The shape line uses the lab's standardized vocabulary, which often differs from how a stone is marketed. Our signature cut, the Dutch Marquise, is an elongated hexagonal cut: pointed ends with straight, angled sides, not the curved navette of a true marquise. On a grading report, you will not see "Dutch Marquise." You will see the lab's geometric description, which for this shape reads "Hexagonal Modified Brilliant" (IGI report, 2026). That is not a discrepancy, it is the lab naming the geometry rather than the brand. For the full definition of the shape, see our Dutch Marquise guide.
It issues no cut grade for fancy shapes, for now. The labs give round brilliants an overall cut grade, but for fancy and elongated shapes that line is currently blank. GIA has announced a fancy-shape cut grading standard arriving in 2027 (GIA, 2025). Until then, on any non-round stone you judge cut yourself from the measurements and proportions, or ask the jeweler to walk you through them. That is reading a stone, not interrogating a seller.
It describes, it does not value. A grading report is not an appraisal and not a statement of price. A diamond is a love piece, something you choose to keep and to mean something, so let the report confirm the facts and let your eye decide the rest.
When to walk away from a certificate
Not every piece of paper is a grading report. The point of buying a graded stone is the independence of the grader, so two kinds of document defeat the purpose. An in-house certificate, graded by the same company selling the stone, is not independent, the seller is grading its own work. An unknown-lab certificate, from a laboratory you cannot find or whose reports do not verify online, gives you nothing to check against. In both cases the document is decoration, not verification.
What you want is straightforward and easy to ask for, with no friction: a report from GIA, IGI, or GCAL, with a number you can confirm on that lab's own site. A good seller offers it before you have to think about it. This is not about treating sellers as suspects. It is about knowing that the stone's description comes from someone with no reason to flatter it, which is exactly what makes you free to buy with confidence.
If you want to take the next step from reading the report to judging the stone in your hand, see our guide to telling whether a diamond is real. Read the report, verify the number, and the most important question (is this stone what it claims to be) is already answered.
About the Author
Jeffrey Bais
Jeffrey Bais oversees jewelry production with precision and dedication. He ensures every piece meets the highest standards of quality and craftsmanship.
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FAQ's
A grading report is an independent gemological lab's description of a diamond. It is not a sales document or an appraisal of value. To read one, look for the lab name, the report number, the 4Cs, the measurements, and the shape line, then confirm the report number on the lab's own website.
In October 2025, GIA moved Lab Grown Diamond reports to two descriptive tiers, "Premium" and "Standard," instead of precise color and clarity grades (GIA, 2025). One result is that an E VS1 and a J VS2 stone can share the same label. IGI still issues the full 4Cs, so it carries more line-item detail.
Read the report number and type it into the issuing lab's own report-check page (GIA or IGI). The online record should match the document line for line. You can also check that the laser inscription on the diamond's girdle reads the same number. Verifying a public report is free and welcome.
A grading report describes geometry in the lab's standardized vocabulary, not trade names. The Dutch Marquise is an elongated hexagonal cut, so a lab report lists it by its geometry, which reads "Hexagonal Modified Brilliant" (IGI report, 2026). That is the lab naming the shape, not a discrepancy.
No. The value of a grading report is the independence of the grader, so an in-house certificate from the seller, or one from a lab you cannot verify online, defeats the purpose. Look for a report from GIA, IGI, or GCAL with a number you can confirm on that lab's own site.
Not yet. The labs grade cut for round brilliants, but for fancy and elongated shapes that line is currently blank, with a fancy-shape cut grading standard announced to arrive in 2027 (GIA, 2025). Until then, judge cut yourself from the measurements and proportions, or ask the jeweler to explain them.