Understanding the 4Cs: The Ultimate Diamond Guide

Everything you need to know about the color, cut, clarity, and carat.

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After stalking your partner's Pinterest boards and harassing friends and family, you've finally pegged the perfect ring design for your future spouse. Or, maybe you two tag teamed the ideal engagement jewel together. Either way, next up comes conquering the famed engagement ring 4Cs and determining how you can manipulate each component to get the most bling for your buck when buying a diamond engagement ring. The 4Cs stand for color, clarity, carat weight, and cut, and they make up a grading system that determines the quality and price of a diamond.

According to gemologist and jeweler Andrew Mills, it's important to note that the 4Cs grading system is a guideline, rather than a "good" or "bad" scale. "The first thing to keep in mind when reading about the 4Cs is that there is no right answer, and a lot of the information out there can be pretty misleading on what is required in purchasing a diamond," says Mills. "What really matters is what YOU think of the diamond and its natural appearance."

Meet the Expert

Andrew Mills is a Gemological Institute of America (GIA) graduate gemologist and founder of Andrew & Earth Designs.

Even if a diamond hits the top of every scale, it will naturally cost the most, but that doesn't necessarily make it any more beautiful than a more affordable diamond. And, all of the 4Cs are factored together, not just individually, when weighing the diamond's value. Essentially, the idea that a diamond has to be "perfect" across all 4Cs is a misconception—there is no "correct" set of diamond specs.

To make your diamond hunting process loads easier, we broke down the specifics of the engagement ring 4Cs in no particular order, along with helpful tips on how to make the most of each component financially.


Photo by Elizabeth Cooney
 Photo by Elizabeth Cooney 

Cut is the only diamond component not influenced by nature, and Mills considers this the most important of the 4Cs. This factor refers to the quality of the diamond's cut, not the shape or size (although these can be interchangeable), and how well the stone is faceted, proportioned, and polished. This also determines how the diamond interacts with light. Brilliance, which is the diamond's ability to return light to the eye, is measured solely by the stone's cut (color and clarity have no impact). For any diamond shape, visually, cut is the first C to consider, followed by color, and, least as important, clarity (as long as the diamond has no visible imperfections).

Per the GIA system, diamond cuts are graded as Excellent, Very Good, Good, Fair, and Poor. Cut grade doesn't influence the cost as much as the other Cs, so Mills suggests always sticking within the Excellent to Very Good range for a well-cut stone that works best with light. "Any range of color and eye-clean clarity will be beautiful and super bright if the diamond is well cut," he says.

The dimension and proportion of a stone (especially for elongated shapes, such as marquise, oval, radiant, emerald, and pear) can majorly influence the look of the diamond. A good rule of thumb is to maintain a well-balanced length to width ratio scale, which can make the stone appear larger. Elongated shapes specifically come in a variety of size ratios, determined by both cut and carat weight, but again make sure to stay within the Excellent to Very Good cut range for the best diamonds.


Photo by Elizabeth Cooney
 Photo by Elizabeth Cooney 

Diamond colors fall under a D-Z scale, with D meaning completely colorless (and the most expensive), and Z having a light yellow hue. According to Mills, standard diamond quality falls within the D-J color grade. The shape of the diamond also influences its spot on the color scale. A round brilliant diamond, for example, hides color incredibly well, meaning you can go further down the scale without seeing any yellowing. However, longer diamond shapes, like oval and radiant, reveal color much easier. Keep in mind, though, diamond color is essentially personal preference and doesn't indicate quality whatsoever.

With round, emerald, and Asscher cuts, you can typically go as low as a J grade without seeing any incredibly noticeable color. On the other hand, cuts such as oval, cushion, radiant, pear, princess, marquise, and heart require quality a bit higher on the scale (G and up) so as not to see any color.


Photo by Elizabeth Cooney
 Photo by Elizabeth Cooney 

This C involves the number of natural imperfections, called inclusions, present in the diamond, and whether you can see them with the unaided eye. The GIA grading scale rates diamonds from Flawless (FL) to Included (I). However, a stone doesn't have to be at the very top of the scale—Flawless or Very Very Slightly Included (VVS)—to look perfect and inclusion-free. It's all about how eye-clean the diamond appears, and Mills says this is what usually surprises people most when viewing diamonds in person. In fact, if an SI1 (Slightly Included) clarity diamond appears perfectly eye-clean, there is no visible difference between a VVS1 (Very Very Slightly Included) clarity stone of the exact same carat, color, and cut—minus about tens of thousands of dollars.

"There is no reason, in my opinion, to go higher than VS1 [Very Slightly Included] clarity for any diamond shape except emerald or Asscher," says Mills. "For all other shapes, starting at SI1 [Slightly Included] clarity and up, you should not normally see any imperfections visible to the naked eye. Sometimes even SI2 diamonds can be very eye-clean, as well, but generally stick with SI1 and up."

To get the most out of your diamond for less, finding a balance between color and clarity is key. While that balance varies by diamond shape, you can save money without sacrificing quality by staying on the high end of the color scale, but the lower end of the clarity scale, as long as there are no visible inclusions.


Photo by Elizabeth Cooney
 Photo by Elizabeth Cooney 

Last but not least, carat refers to a measurement of the actual weight of the diamond. According to GIA, one carat converts to 0.2 grams, which is essentially the same weight as a paper clip. Naturally, the larger the carat, the more expensive the diamond. Because no two diamonds are completely identical, carat should be viewed as a guideline, since it only determines the weight of the stone as opposed to the actual size. "You can have five diamonds, let's say oval, all exactly 2.00 carats, all the same color, clarity, and cut, but they will all be slightly different sizes and shapes," Mills explains.

A diamond carat is divided into 100 points, meaning a 50-point diamond weighs 0.50 carats. However, a stone with a certain weight may actually look larger than the carat suggests due to its dimensions (measured in millimeters). For example, you could potentially find a diamond that weighs 2.00 carats but appears closer to a 2.20 carat stone. Essentially, you're buying a stone that looks larger without the extra cost associated with a higher weight.

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