What Happens When the Same Lab Diamond Is Graded by Both IGI and GIA

Submit the same lab-grown diamond to both IGI and GIA, and the two reports will often show different color and clarity grades for the identical stone. The gap tends to run about one grade in each category: a stone IGI calls VS1/G might come back from GIA as VS2/H. That one-grade difference has real consequences for price, perceived quality, and which report you can actually use in 2026.

The reason this matters now is that the grading landscape shifted in late 2025. GIA stopped issuing traditional 4C letter grades for lab-grown diamonds entirely, replacing them with a two-tier “Premium or Standard” quality assessment. IGI kept its full grading system intact. So the comparison is no longer just about strictness; it is about whether a comparable report exists at all.

How strict is each lab when grading the same stone?

IGI grades are generally considered slightly more lenient than GIA for color and clarity. A stone graded VS1/G by IGI might receive VS2/H from GIA, a consistent pattern the industry has observed for years. One useful framing: an IGI “VVS2/E” lab-grown diamond is roughly equivalent in real-world appearance to what GIA would have called a “VS2/F.”

That said, the relationship is not perfectly one-directional. Analyses of dual-certified stones (diamonds submitted to both labs) show mixed results. In some documented cases, GIA graded a stone as J color while IGI called it I, which fits the expected pattern. In other cases, the opposite happened: IGI returned a G while GIA returned an F. Four out of six stones in one small analysis received identical grades from both labs. The honest conclusion is that IGI tends to run slightly looser on average, but individual stones can land anywhere, and the sample of dual certified lab diamonds is far too small to treat the one-grade gap as a guarantee.

What is consistent is this: both labs examine color on the D-to-Z scale and clarity from Flawless to I3. They use the same framework. The difference is in where each lab draws its internal boundaries within each grade category.

Why did GIA stop issuing 4C grades for lab diamonds?

On June 2, 2025, GIA announced it would no longer apply its traditional 4C grading system to lab-grown diamonds. Effective October 1, 2025, every lab-grown diamond submitted to GIA receives a simplified “Quality Assessment” rather than letter grades. Stones are placed into one of two categories: Premium (D color, VVS clarity or higher, Excellent polish and symmetry) or Standard (E-to-J color, VS clarity or higher, Very Good polish and symmetry). Anything that falls below Standard receives no designation at all.

GIA’s stated reasoning was that more than 95% of lab-grown diamonds entering the market already cluster in a very narrow range of high color and clarity, which makes fine distinctions between individual letter grades less meaningful for consumers. Critics read it differently: as a signal that GIA wants to distance itself from the lab-grown category and protect its core identity in the natural diamond market.

For buyers, the practical effect is straightforward. A GIA report on a lab-grown diamond today tells you whether a stone clears a quality threshold. It does not tell you whether a stone is D or E, or VVS1 versus VVS2. IGI continues to issue those specific grades, which is why the large majority of lab-grown diamonds on the market now carry IGI reports.

What does the grade gap mean for price?

A GIA-certified lab-grown diamond (when such reports existed in full 4C form) typically sold at a modest premium over a comparable IGI-certified stone, even when the actual diamonds were similar in quality. Part of that premium reflected GIA’s brand recognition; part reflected the stricter grading, which meant a GIA VS1 was likely a cleaner stone than an IGI VS1.

Under the new system, that price dynamic has changed. IGI now holds the only full 4C report available for lab-grown diamonds, which gives it practical dominance in the category. IGI began certifying lab-grown diamonds in 2005 and has graded millions of them since, building extensive calibration data specific to the category. That experience matters when a buyer wants to know not just “is this Premium quality” but exactly where a stone sits on the color and clarity spectrum.

For shoppers, the takeaway is that an IGI grade of VS1 or higher in clarity, and G color or higher, tends to produce an eye-clean stone that holds its visual quality well. Buyers who want the most specific quality information available in 2026 will find it on an IGI report, not a GIA one.

How should you use this information when buying?

Knowing the grading gap changes how you read a certificate. If you are comparing two lab-grown diamonds with identical stated grades from different labs, the issuing lab affects how precisely to interpret those grades. Two stones both labeled VS1/G are not necessarily the same; one IGI VS1/G and one GIA VS1/G (from before October 2025) may represent slightly different actual quality levels, with the GIA stone likely sitting closer to the stricter end of the VS1 range.

A practical floor worth applying when shopping IGI-certified stones: target VVS2 or better in clarity and F or better in color if you want a stone that will look clean to the naked eye and hold its value well. For SI1 and below on an IGI report, it is worth requesting actual images or video, since those grades can occasionally produce stones with visible inclusions.

The most important step with any report is verification: confirm the report number directly on igi.org before completing a purchase. Any retailer worth buying from will provide a verifiable IGI report number, so you are never relying on a seller’s description alone.

The Grade Gap Is Real, but the Diamond Beneath It Does Not Change

When the same lab-grown diamond goes through both IGI and GIA, the grades often differ by about one step in color and one step in clarity, with IGI typically returning the higher result. That gap does not change the physical stone. The light performance, the chemical composition, the visual appearance under normal viewing conditions: none of that shifts because of which lab issued the report.

What the gap does change is how you read a certificate and what quality floor you set when shopping. Since GIA no longer issues 4C grades for lab-grown diamonds as of October 2025, IGI is now the primary source of specific, actionable grading data for this category. Setting a quality floor of VVS2/F or better on an IGI report, and verifying the report number before purchase, gives you the protection that the old GIA comparison used to provide.

Frequently Asked Questions

Does IGI always grade more leniently than GIA for lab-grown diamonds?

IGI tends to run about one grade higher than GIA on average for both color and clarity, but it is not a guaranteed rule. Analysis of dual-certified stones shows cases where GIA returned a higher grade than IGI. The gap is a useful planning assumption, not a fixed formula, and individual results vary by stone and grading session.

Can I still get a GIA 4C grade for a lab-grown diamond in 2026?

No. Effective October 1, 2025, GIA stopped issuing traditional 4C letter grades for lab-grown diamonds. Stones submitted to GIA now receive a “Premium” or “Standard” quality designation instead of specific color and clarity grades. IGI remains the primary lab issuing full 4C reports for lab-grown diamonds.

If an IGI grade runs higher, does that mean IGI-certified diamonds are lower quality?

Not necessarily. The physical diamond is the same regardless of which lab grades it. A higher IGI grade relative to GIA reflects where each lab sets its internal grade boundaries, not a difference in the stone itself. The practical implication is to set a slightly higher quality floor when buying IGI-certified stones, targeting VVS2 or better in clarity to ensure the stone is genuinely eye-clean.

What is a dual-certified lab diamond, and are they worth seeking out?

A dual-certified diamond carries grading reports from two different labs, typically both IGI and GIA. They are rare in the market. When they do appear, they offer useful insight into how the two labs compare on the same stone, but the sample size of publicly documented cases is too small to draw firm conclusions. For most buyers, a single verified IGI report is sufficient.

How do I verify an IGI certificate is genuine before buying?

Go to igi.org and enter the report number printed on the certificate. IGI’s online database will return the full grading details for that specific stone. If the number does not appear or the details do not match what the seller described, do not proceed with the purchase. This step takes under two minutes and is the single most effective protection against report fraud.