The Ultimate Guide to the 4Cs of Diamonds

How to choose the right stone for you.
Diamond engagement ring and wedding band
Photo: Mark S Johnson / Shutterstock
Naomi Rougeau
Naomi Rougeau
Naomi Rougeau
Naomi Rougeau
Senior Fashion and Beauty Editor
  • Naomi writes and edits articles for The Knot Worldwide, specializing in fashion, jewelry, and beauty.
  • She brings over a decade of experience as a writer, editor, and creative consultant.
  • Prior to The Knot Worldwide, Naomi was the senior fashion features editor at ELLE Magazine, where she also oversaw the publication's living and travel sections.
Updated Apr 10, 2024

When you begin researching the perfect diamond engagement ring, you'll be presented with endless information about diamond shapes and varieties, ring metal types, settings, and much more. As you dive deeper into the process of buying an engagement ring, you'll eventually be met with the 4 Cs. Most, if not all, shopping guides and jewelry websites include information about the 4 Cs. And if you're particularly new to diamond sourcing, you might be left wondering what they are, and if they really impact your final selection. (Spoiler alert: they do!)

Before we define exactly what the 4 Cs of diamonds are, it's helpful to know their origin, as well as why they matter. "The 4 Cs are the standards by which all diamonds are evaluated, and they play a role in determining a diamond's value and beauty," explains De Beers Diamond Expert Kristen Lawler-Trustey. All diamonds are evaluated using a standard grading scale developed in the 1950s by the Gemological Institute of America (GIA). The 4 Cs are cut, color, clarity and carat, and the grading reports are compiled to determine a diamond's quality and price.

While these are important characteristics, don't stress about becoming a 4 Cs expert just because you're in the market for an engagement ring. While it's helpful to know the background of the 4 Cs before you shop, any jeweler or ring designer should be able to guide you through the process. "You can—and should—ask your jeweler questions about the 4 Cs," says Boston-based jeweler Hannah Florman. "While you should do some research beforehand, your jeweler is an expert. These characteristics are only meant to be a guiding tool to make sure that you get a quality ring."

Below, we explain the 4 Cs of diamonds in order of importance to help you feel confident in your engagement ring shopping experience. As soon as you're ready to take the next step, you'll want to check out The Knot Vendor Marketplace to locate a reputable jeweler near you.

Meet the Experts

  • De Beers diamond expert Kristen Lawler-Trustey has honed her eye for quality after nearly a decade at the famed South African firm, which is known for creating some of the finest diamond jewelry on the market.
  • Christina Gandia Gambale, co-owner of Greenwich St. Jewelers. The second-generation, family-owned company is celebrating its 47th year of helping to-be-weds find their perfect rings.
  • Payal and Kajal Vitha, co-founders of Los Angeles-based brand Sonu Company, which aims to provide a more sustainable and transparent journey for bespoke engagement rings and fine jewelry.
  • Master jeweler Donna Distefano got her start as the senior goldsmith for the Metropolitan Museum of Art in New York City. A champion of natural diamonds, her work boasts a celebrity fanbase that includes Johnny Depp and Debbie Harry.

In this article:

The 4 Cs of Diamonds to Know For Your Engagement Ring

It's a term that gets bandied about quite a bit and for good reason. But are the revered 4 Cs and the diamond color scale the be-all and end-all when it comes to selecting the best engagement ring for yourself or your partner? That all depends on your goals and aesthetic, among other factors. Generally speaking,

What is a Diamond Grading Scale?

Cut, Color, Clarity, and Carat. Easy enough to remember but more nuanced upon closer inspection. After all, this is Mother Nature you're dealing with (if it's a natural diamond you're after and not a lab-grown diamond). The order in which they're most often mentioned is also significant as it reflects the order or priority. Contrary to popular belief, a bigger diamond is not necessarily better. "I find my customers are responding to quality, and I'm loving that," says Donna Distefano. "They are not necessarily coming to me just to buy a big stone because they want something big, so their focus is on quality over quantity, and that's music to my ears."

Using the Diamond 4 Cs to Choose Your Engagement Ring

For most shoppers, getting to know the 4 Cs means coming to terms with certain tradeoffs and that's OK. Rare is the to-be-wed who can spring for the most flawless stone available without compromising on size. In fact, it's not unheard of for couples who opt for lab-grown diamonds in order to procure a larger stone to trade in for a smaller or less perfect model down the line. There's an element of believability at play relative to lifestyle and budget and perhaps it's better to save the grand flourishes to costume jewelry. At the end of the day, your diamond has to speak to you, not everyone within eyesight.

Diamond Cut

Among the 4 Cs, cut grade is by and large the most important. Why? It is the biggest factor in determining a diamond's brilliance. "If you want your ring to sparkle, it's important to pay attention to the cut," says Florman. "Although it's often overlooked, the cut is extremely important as it refers to the craftsmanship and quality of a diamond."

It's a common misconception that the cut of a diamond is also its shape (like an oval, emerald, pear, or cushion), but there is indeed a difference between the two. "The cut refers to the cutting and polishing of the diamond, which determines both the shape and the way the light reflects and refracts within the diamond, creating brilliance, fire, and scintillation to the naked eye," explains Lawler-Trustey.

If the diamond is cut too deep or too shallow, it will leak light on the sides, giving it a lackluster appearance, which will reduce its value and brilliance. A well-cut diamond will have two factors: mirror-like facets and a "white light" reflected both internally and externally, also known as brilliance, or what will make an engagement ring shine bright.

Diamond Color

Next on the list of 4 Cs is color. And while you might assume that all diamonds have no tint, they're actually graded on a scale of colorlessness—and this characteristic has a direct influence on the value of a diamond. "The GIA also grades diamonds based on their absence of color," Florman shares. "This scale ranges from D, which is completely colorless to Z which is a light yellow to brown."

And, as with the other Cs, the color grade impacts the cost of the diamond. "The closer a diamond is to a grade D, the more expensive it will be," Florman adds, noting that it's possible to move on the scale without sacrificing quality. "Staying in the 'near colorless' range with a G, H, I, or J diamond will give you the best value, however, it is important to keep in mind that shapes and cuts show color differently. For example, rounds and emeralds can hide color well whereas ovals and cushions show it more."

If the diamond color scale sounds a bit confusing, don't stress. According to Payal and Kajal Vitha, co-founders of Los Angeles-based brand Sonu Company, there's a simple way to understand this C: "The most important thing to remember is that the earlier in the alphabet, the less visible color."

Diamond Clarity

Clarity is the next most important factor of the 4 Cs of diamonds, and it determines the number of imperfections within the stone. "Clarity is the measure of a diamond's natural inclusions or imperfections," says Lawler-Trustey. "The standard 4 Cs grading system divides clarity into five distinct groups; Flawless (FL), Very Very Slightly Included (VVS), Very Slightly Included (VS), Slightly Included (SI), and Included (I)."

It's helpful to know that inclusions aren't necessarily the sign of a "bad" diamond. In fact, these spots can be somewhat common as they occur when a natural diamond crystallizes in the earth's mantle under intense heat and pressure. The same can happen to lab-grown diamonds too—since they're created through a process that mimics the environment of the earth's mantle, these stones are also prone to inclusions.

So, what makes for a "good" diamond clarity grade? It's a bit more complicated than just picking one measurement. "It's important to know that just because two diamonds share the same clarity grade does not mean they will look the same," says Christina Gandia Gambale, co-owner of Greenwich St. Jewelers. "In fact, they can appear very different. This is because clarity is graded according to three factors: the amount of natural inclusions, where they are located within the diamond, and how dark or light they are."

Diamonds that are considered to be "internally flawless" will be much more expensive, especially because they're extremely rare. When it comes to finding an engagement ring in your budget, the Vitha sisters recommend being flexible in this category. After all, many inclusions aren't visible unless they're viewed under 10x magnification. It's completely possible to opt for an "eye clean" diamond, which appears flawless to the naked eye, with inclusions only visible under magnification. "When it comes to clarity, we always urge our clients to choose what fits their budget," they say, noting that just because a diamond has a lower clarity rating doesn't mean its blemishes will be particularly visible to the naked eye. "Clean SI and VS clarity grade diamonds are our most popular choices because they cost much less but are equally as gorgeous."

Carat Weight

Finally, carat refers to the weight of the diamond. As the diamond carat size increases, so does its rarity and, of course, the price tag. "A carat is how the jewelry industry measures a diamond's weight," Florman shares. "Although some diamonds may have the same carat weight, they can appear different due to how they're cut. The number of carats can also make a huge difference in price, even if it's just a tenth of a carat. Choosing a diamond slightly below popular carat weights like 1.5, 2, 2., and 3 can offer great savings."

While you might assume that a higher carat weight correlates to a larger diamond, that's not always the case. Certain diamond shapes can appear larger than their carat weight because of the surface area they take up on the hand. "Rounds, emeralds, ovals, and pears appear largest for their weight while cushions appear smallest," Florman adds. The depth of the cut will also impact the appearance of its size, as a diamond with a smaller carat size but a shallow cut may look larger than a diamond with a bigger carat size and a deeper cut.

The appearance of size all depends on the shape of the diamond, as well as the different designs and mountings you choose—a halo will make a smaller stone appear larger, for example, and so will a shape with more surface area, like a pear or emerald.

So, now that you're a budding expert on the 4 Cs, how can you use this information to pick the perfect stone? Experts say it all comes down to your personal preference, as well as what diamond price fits in your budget. "The perfect diamond does not only mean being at the high end of the 4 Cs," says Gambale. "Finding the perfect diamond means understanding your priorities when it comes to your diamond's appearance." This is especially important to remember if you're in the market for a non-traditional stone, like a salt and pepper diamond, for example. Although its 4 C grade tends to be lower, the unique color and gradient are actually desirable for some.

Finding the perfect stone is all about following your own aesthetic while using the 4 Cs as a guide, rather than a rulebook. "Work within the 4 Cs to find the perfect balance that will maximize beauty and value," Gambale adds. "One size does not fit all when diamond shopping, so an experienced professional or gemologist will help you navigate the Cs to pick the diamond for you."

Going Beyond the 4 Cs of Diamond Grading

"When people are shopping for diamonds, they're not going to enroll in Gemological Institute of America and become gemologists, and I don't recommend that," says Donna Distefano. "it's a lot of work, but I think they should look at a GIA certificate and learn a little bit more beyond the 4 Cs." Among the biggest additional factors: fluorescence.

Polish and symmetry are important, to be sure. But when a diamond has a lot of fluorescence, that's not a good thing because it means there's a lot of color bouncing in and out and the goal is to procure the most colorless (we're discussing white/clear stones for this article) diamond you can. "Polish and symmetry come next," explains Distefano. "You might have something with these excellent four Cs happening, but what if it has a horrible polish, or what if the symmetry is wrong?" If the price seems too low, that might be why you're getting a deal. At the end of the day, the best approach (according to Distefano) is to find an expert you trust and try to let go of the reigns a little bit. Learn as much as you can, but let the diamond speak to you.

Sarah Hanlon contributed to the reporting of this article.

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