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The Complete 4Cs of Diamonds Guide: What Changed for Lab-Grown in 2026
4Cs of diamonds is the core concept in Diamonds industry, so let’s dive deeper into them. Anyone who has bought a diamond will tell you about the 4Cs: cut, colour, clarity and carat. This is what every jeweller, every accreditation and every price tag is based on. A lot of guides don’t explain that the rules for lab-grown diamonds changed in 2025, and if you are looking to buy one at the moment, this change affects how you should interpret a grading report. This guidebook will walk you through the 4Cs as defined by GIA, and how they differ when the gemstone in front of you is lab-created.
Quick answer
The 4Cs are cut, color, clarity, and carat weight. As of October 1, 2025, GIA no longer issues individual color and clarity grades for lab-grown diamonds, only a Premium or Standard tier. IGI still issues full, individual grades for lab-grown stones.
What Are the 4Cs of Diamonds?
In the 1940s, GIA founder Robert Shipley developed the 4Cs: Cut, colour, clarity and carat weight, to help consumers distinguish diamonds. Over the following decades, GIA extended the concept into a complete grading system, adding the D to Z colour range in the 1950s and introducing a unique cut grading system for round brilliant diamonds in 2006. The 4Cs are the internationally accepted standard for determining diamond quality and are used by GIA, IGI and all reputable labs in the industry for both natural and laboratory grown gems.
Cut: The Most Important C
Of the four criteria that determine how a diamond looks, cut is the most important. The cut is the only characteristic of a diamond that can be altered by an individual, and it affects how the stone reflects light as brilliance, fire and scintillation, whereas colour and clarity are inherent attributes. An Excellent cut diamond will sparkle more than a larger diamond with a worse cut, since it reflects more light that hits it. GIA grades diamonds on a scale from Excellent to Poor, while IGI uses an equivalent Ideal to Poor method. If on a tight budget and forced to choose between the 4Cs, cut stress.
Color: The D to Z Scale Explained
Diamond colour grading refers to how close the stone is to being colourless and not to the strength of the hue. The grading scale is from D, which is completely colourless and the rarest, to Z, which has a noticeable yellow or brown tint. Most buyers will choose stones around the G to J range for engagement rings as they look almost colourless but will be far less expensive than D or E grade diamonds. Lab-created diamonds are commonly made at the high end of this range, which has caused GIA to change the way it reports colour for lab-grown diamonds, as detailed below.
Clarity: The FL to I3 Scale Explained
Clarity refers to the internal and exterior faults of a diamond, from Flawless, with no inclusions visible at 10x magnification, to Included, where blemishes are visible with the naked eye. Most of the grading range from VVS to SI1 is concerned with defects that are invisible to the naked eye, and require a jeweler’s loupe to see. With the naked eye, you may not be able to see the difference between a VS1 or SI1 diamond and a flawless diamond, and this is where many buyers find huge discounts.
Carat: Weight, Not Size
Carat is a measurement of weight, not size. One carat is 200 milligrams. The size of two diamonds of the same carat weight may differ in their cut and shape. A well-cut diamond will spread its weight across a wider area that can be seen. A deep diamond that is not cut well may be heavier, yet appear small from the top. The first thing that most buyers notice is the carat, and this is something that should be considered in relation to the cut, not pursued on its own.
The 2025 Shift: Why GIA Stopped Giving Lab-Grown Diamonds Detailed Grades
Most of the 4Cs manuals have not yet dealt with this. Effective 1 October 2025, GIA will stop issuing specific D-Z colour classifications and FL-I3 clarity grades for lab-grown diamonds. Instead, all GIA-graded laboratory-grown gemstones now fall into one of two categories.
- Premium: D-equivalent color, VVS clarity or better, Excellent polish and symmetry, and for round brilliants, an Excellent cut grade
- Standard: E to J color, VS clarity, Very Good polish and symmetry (Good permitted for some fancy shapes), and Very Good cut for round brilliants
A lab-grown diamond that does not meet the Standard threshold does not receive a GIA report at all.
GIA’s rationale for the change is simple. The vast majority of lab-grown diamonds on the market are generally in a narrow range of colour and clarity, with more than 95 per cent of them, so the full grading system developed for the wide natural variation of mined diamonds cannot effectively differentiate between the lab-grown stones. Natural diamonds are still immune. GIA continues to offer complete 4Cs assessments for these.
What This Means for You as a Lab-Grown Buyer
If the lab-grown diamond you’re considering has a GIA report, it is a Premium or Standard grade, not an actual colour and clarity grade. This is not a danger sign; GIA’s own statistics show that the output of lab-grown diamonds is stable enough to merit a two-tier classification. However, this means you’re getting less detail than an IGI report, as IGI continues to record the specific colour grade, clarity grade, and the cut, polish and symmetry of lab-grown gemstones. In our extensive guide on IGI versus GIA (link to be added once published), we break down the IGI vs GIA comparison on lab-grown diamonds, and talk about why Culture Carats prefers IGI certification.
How to Actually Use the 4Cs When Shopping
First, set a clear goal, as this is often the primary driver of the budget. Most importantly, emphasise the cut in that budget, as it has a big impact on the appearance of the stone. Most people without gemological knowledge will consider a G to J colour and VS2 to SI1 clarity to be eye-clean and essentially colourless; therefore, shifting money from colour and clarity is often the easiest way to a better cut or a bigger stone.
Browse our full loose diamond selection, or start with Round, the most classic cut and the shape with the most standardized cut grading available.
FAQ
What are the 4Cs of diamonds?
Cut, color, clarity, and carat weight are the four characteristics GIA established in the 1940s to describe and grade diamond quality.
Which of the 4Cs matters most?
Cut. It has the largest effect on how a diamond looks, since it determines how well the stone returns light as brilliance and sparkle.
Does GIA still grade lab-grown diamonds by color and clarity?
No. As of October 1, 2025, GIA replaced individual color and clarity grades for lab-grown diamonds with a two-tier Premium or Standard system.
What is the difference between GIA Premium and Standard for lab-grown diamonds?
Premium requires D-equivalent color, VVS clarity or better, and Excellent polish, symmetry, and cut. Standard covers E to J color, VS clarity, and Very Good or better polish, symmetry, and cut.
Does IGI still give detailed color and clarity grades for lab-grown diamonds?
Yes. IGI continues to issue individual color and clarity grades for lab-grown diamonds, the same way it grades natural diamonds.
What carat, color, and clarity should I look for in a lab-grown diamond?
For most buyers, G to J color and VS2 to SI1 clarity look eye-clean and colorless while leaving more budget for a better cut or a larger carat weight.
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