4Cs of Diamond | GIA Diamond Grading Guide

4Cs of Diamond | GIA Diamond Grading Guide

4Cs of Diamond | GIA Diamond Grading Guide

Posted by Sharif Khan on 3rd Jul 2021

Diamond is among the world's most valued natural resources and highly desired gemstones. It is naturally made with an enormous variety of characteristics, making each diamond unique. The combinations of these characteristics determine the quality and value of a diamond.

The Four Cs stand for Cut, Color, Clarity, and Carat Weight. The diamond grading system has transformed the diamond trade and is currently used by nearly every professional in the industry and diamond enthusiasts worldwide. Because diamonds vary immensely in quality and price, consumers need to be familiar with the Four Cs. We have outlined the basics of this grading system below to help consumers learn the resources they need to make informed purchases.

The 4Cs—diamond carat weight, diamond color, diamond clarity, and diamond cut—are the most critical factors that play a critical role in determining a diamond's price. While the first three are natural elements, the fourth depends on the craftsmanship quality since it is a human factor. We also consider three other factors to be critical in determining a diamond's value, including diamond shape, diamond fluorescence, and diamond certification.

Here are some essential points you should consider while reviewing each C:

James Allen

Diamond Carat Weight: This is simple and straightforward to understand; the bigger the stone, the higher the price. However, there is a catch. The price of a 2-carat diamond, all other factors being equal, is not twice as much as a 1-carat diamond's price. It would be most likely three to four times the price of a 1 carat because scarcity plays a considerable role in how diamonds' prices are determined. Because a 2-carat diamond is scarcer than a 1-carat diamond, its price would be significantly higher.

Hint: Look for stones that are not a full carat, e.g., .95ct or 1.95ct, because diamonds' prices tend to jump once they hit a full carat.

Diamond Cut: Diamond cut is probably one of the most critical factors in how the diamond is priced, affecting its overall brilliance and fire. It is a human element often manipulated to save as much weight of the rough diamond as possible. Diamond cut ranges between excellent, very good, good, fair, and poor. The GIA assigns a cut grade for round brilliant cut diamonds, and for fancy shape stones such as an oval cut or a princess cut diamond, it has yet to finalize a grading system. However, there are important insights that we have developed for each shape stone that you should read before buying a diamond.

Hint: The most crucial factor in the cut of a diamond is depth, table, girdle size, crown angle, pavilion angle, and culet. Ensure that you know enough about these factors, especially table and depth, before buying a diamond. It is okay to compromise on the cut of a diamond slightly if the stone's brilliance or fire is not compromised, though you must not compromise more than 3-5% as it is a crucial factor.

Diamond Clarity: Clarity is one of those factors that you can play with depending on your budget. Diamonds are formed over millions of years under intense heat and pressure and, as a result, often have impurity and inclusions. These inclusions are the stone's natural birthmarks and are often evaluated to determine each diamond's level of clarity. Clarity ranges between Flawless (Fl), Internally Flawless (IF), Very Very Slightly Included 1 & 2 (VVS1/VVS2), Very Slightly Included 1 & 2 (VS1/VS2), Slightly Included 1 & 2 (SI1/SI2), and Included 1,2 &3 (I1, I2, I3). Stones above VS2 that the GIA grades are often considered eye-clean, implying that you may not see any inclusions in the diamond without the aid of a jeweler’s loupe. In under 1-carat stones, SI1 and SI2 would be considered eye-clean. I-I3 are almost always not eye-clean unless the diamond has large black crystals.

Hint: Because SI1 diamonds are eye clean at times, it gives you plenty of space to make a compromise if you are on a budget to get a lower clarity grade diamond.

Diamond Color: In white diamonds, color is probably the second most important factor after the cut of a diamond. The absence of color makes the diamond more desirable; therefore, the lower the yellow tint, the better the diamond. Color grade ranges from D to Z where a completely colorless diamond would obtain the higher color grade of D. Colorless range is D-F, Near Colorless range is G-J, Faint range is K-M, Very Light Yellow Range is N-R, and Light Yellow is S-Z.

Hint: G is an excellent color even for an investment-grade diamond, but if you are on a budget, going as low as I/J is not a wrong choice. Also, in lower color grade diamonds, e.g., H, I, J, buy diamonds with blue fluorescence as it can make the diamond look whiter than it is because blue is a complementary color to yellow.

Detailed Insights on 4Cs of Diamond

It is imperative to note that you would have to learn more about each C to understand how vital a particular C is while considering a diamond. Please also note that there could be a big difference between a diamond with the same grading in terms of the 4Cs, which is why understanding each C's details is essential.


Like the cut of a diamond, its color will either increase or decrease its sparkle and fire. A diamond with less color will reflect more light than those with a light yellow or brown hue. This, coupled with the fact that nature provides us less of these colorless diamonds, makes them more valuable and sought after.

The most common color grades are G through I since they are more abundant and affordable. Although diamonds of these grades do have a hint of color, it generally is not visible to the naked and untrained eye.

Diamonds are graded according to the GIA (Gemological Institute of America) color chart:

D,E,F: Colorless. Stone looks completely clear. These are the highest-priced stones. Approximate price for VS1 Clarity, one carat round diamond: $15,000

G,H,I,J: Near Colorless. Some yellow or brown color is visible when the stone is not mounted. When mounted, the stone appears colorless. This range is considered an excellent value for the money. Approximate price for VS1 Clarity, one carat round diamond: $10,000

K, L, M: Light Yellow. Yellow tint shows. When mounted, this still appears tinted. Approximate price for VS1 Clarity, one carat round diamond: $5,000

N-Y: Yellow. Strong yellow color. These stones are not used in fine jewelry. Approximate price for VS1 Clarity, one carat round diamond: Less than $3,500

Z+: Fancy. Bright, remarkable color. Usually blue, pink, yellow, etc. Approximate price for VS1 Clarity, one carat round diamond: More than $10,000.


According to the GIA, "diamond clarity refers to the absence of internal inclusions or external blemishes." Of all diamond characteristics, clarity may significantly impact a diamond's value since a flawless diamond is rare. Natural diamond is created deep within the earth under extreme pressure, and so it is not surprising that nearly all diamonds have minor flaws. There are two types of flaws - blemishes and inclusions. Blemishes are external flaws found on the surface of a diamond and include chips, nicks, and scratches, most of which occur during the cutting process. Inclusions are internal flaws such as bubbles, cracks, or other minerals within the center of the diamond.

GIA developed a universal diamond clarity grading scale consisting of 11 grades. Diamond is graded under 10x magnification, so most of the flaws that affect the clarity grade are barely visible to the naked eye. In addition to the number, size, and severity of the inclusions, the inclusion's position and color are also considered when grading the clarity of a diamond. Since no two diamonds are alike, a diamond's characteristics and its inclusions make it unique and sometimes used, like fingerprints, to identify the diamond.

The clarity grades are flawless and internally flawless: diamonds of these grades are valuable because they are rare. The next best clarity grades are VVS (very, very slightly included) and VS (very slightly included). These diamonds are more common and sought after because they are more affordable than flawless ones, though they have minor inclusions, most of which can only be seen under magnification by a skilled grader. The most common clarity grade is likely SI (slightly included). A diamond of this clarity is still considered "eye-clean" and provides an inexpensive alternative. The lowest clarity grade, I (imperfect), has more noticeable inclusions, affecting a diamond's brilliance.

The GIA defines their clarity grading scale as follows:

Flawless (FL)

No inclusions or blemishes are visible to a skilled grader using 10x magnification.

Internally Flawless (IF)

No inclusions and only minor blemishes are visible to a skilled grader using 10x magnification.

VVS1 and VVS2

Very Slightly Included (VS1 and VS2)

Slightly Included (SI1 and SI2)

Imperfect (I1, I2, and I3)


Diamond cut is one of the "four Cs" used to determine the overall quality and, therefore, a diamond's price. Most diamond certificates will include a rating of the diamond's cut, and, all other things being equal, a diamond with a better cut grade will command a higher price.

The methods for determining a diamond's cut rating can vary depending on who is making the assessment. To further complicate the matter from the buyer's perspective, some certificates do not explain in much detail what criteria they used to grade a diamond's cut.

That having said, if you are thinking of buying a diamond, it would be well worth the time it takes to understand what different cut grades mean, how they are determined, and what influence they have on a diamond's price. This knowledge makes you better able to determine for yourself what a diamond's price should be, distinguish a good deal from a bad one, and make the best possible investment when buying diamonds.

In simple terms, the cut grade of a diamond refers to a diamond's "light performance," meaning the degree to which the diamond retains and reflects the light that enters it. A diamond with a good cut will be highly reflective and exhibit the best possible amount of sparkle. Conversely, diamonds that "leak" light through the bottom or side are usually cut too shallow or deep, respectively, and they will thus have a less favorable cut grade.

Since it is widely acknowledged that the aforementioned sparkle or brilliance gives diamonds their unique beauty, it follows that cut is what separates the most stunning diamonds from just ordinary ones.

It should be noted that "cut" in this sense does not refer to the intended shape of the diamond. If you have ever browsed for diamonds, you have probably come across terms like "Princess cut," "Asscher cut," "Emerald cut," and so on. These refer only to stylized diamond shapes and are not an indication of a cut rating.

The diamond's cut is a large part of why it shines so brightly and looks so beautiful. An ideally cut diamond reflects the light up toward the viewer's eyes, causing the diamond to look bright and shiny. If a diamond is cut "shallow" or the distance from the table to the cutlet is shorter than it should be, the light will be reflected away, and the diamond will be less brilliant. Similarly, if the diamond is cut too deep, the light will shine out of the pavilion and will not make the top (table and crown) appear bright and lovely.

The cut can enhance the overall quality, value, and beauty of that diamond.

Various cuts remarkably affect the following three qualities:

Brightness: The amount of light the diamond reflects.

Fire: The several colors of the range that a diamond gives off.

Scintillation: The sparkle and brilliance that is produced when a diamond is moved.

In a well-cut diamond, the light that enters through the table (the top flat facet) and travels through to the pavilion is then reflected and dispersed through the crown, creating a desirable effect. Unfortunately, in a poorly cut diamond, some of the light leaks out the girdle, which dramatically reduces the diamond's sparkle.

A diamond cut's quality is based primarily on symmetry, polish, and the proportions of the table size, crown angle, and pavilion depth to one another. In most cases, the more facets a diamond has, the more brilliance and sparkle it will have. However, the depth of the pavilion also has a massive impact on this. When the pavilion's depth is either too much or not enough, the light can be lost out the sides of the stone instead of being directed through the crown.

The brilliant round cut diamond is the most common of the diamond cuts, although many others are gaining popularity. The brilliant round cut was explicitly designed for use on the diamond, and with its 57-58 well-proportioned facets, its brilliance and sparkle are more noticeable than on most cuts. Yet, there are many variations of diamond cuts and combinations of proportions, directly affecting the beauty of a diamond and its value.


At this point, there is not a standardized system for diamond cut grades. Each certifying authority uses its system to rate the cut of a diamond, making things slightly confusing. Thankfully, however, the grades themselves are usually reasonably self-explanatory, even if the methods used to determine them are not clear (more on this later).

Most certifiers use a five or six-point cut grading system. The typical system goes as follows, from best to worst:

Ideal: A diamond with maximum brilliance.

Premium: Nearly equal to Ideal.

Very Good: A diamond with slight light leakage.

Good: A diamond with decent reflectiveness, usually one which has been cut for size rather than brilliance.

Fair or Poor: Diamonds that reflect relatively little light.

Again, though the terminology used can differ in some cases, the Gemological Institute of America, one of the significant diamond rating authorities, grades diamond cuts as Excellent, Very Good, Good, Fair, and Poor. Hence, diamond cuts rated "Excellent" by the GIA will be roughly equivalent to those rated "Ideal" by other bodies. Additionally, some diamond vendors have a special designation for their best cuts. For example, the online diamond retailer Blue Nile has a "Blue Nile Signature Ideal" cut, a term they use to refer to cuts within the top 1%.


A diamond's weight is measured in carats, with one carat equaling 200 milligrams or one-fifth gram. You may also hear the term "points" used when speaking of diamond weight. One carat is divided into 100 points, and so a one-fourth carat diamond would be referred to as a '25 point diamond.'

Although carat weight is also used to measure gemstones, it is slightly more complicated since gemstone types may have different densities.

When written, carat is usually abbreviated as "ct." In a jewelry piece with several diamonds, the abbreviation used is "ct TW," meaning carat total weight (the sum of each diamond's carat weights). However, it is usually shortened to "ctw." The value of such a jewelry piece may be less than that of a similar item of the same carat weight with only one diamond. Diamond solitaires are rarer, and therefore, a 1ct Diamond Solitaire ring will be worth much more than a similar 1ctw ring with a smaller diamond.

Likewise, diamonds of the same carat weight and size might not be the same value because one may have better color or clarity than the other. The cut of a diamond has a significant effect on diamond value and carat weight; hence some diamond cuts hold more volume than the other diamond.

The Four C's as outlined above are the main characteristics that affect the value of a diamond. However, just as important is that they classify the diamond's unique beauty and standardize the grading system used to classify the diamond's quality. We highly recommend that consumers educate themselves about diamond grading and other related jewelry info.