What You Really Need to Know About the 4C's of Diamonds, According to Experts

Is one "C" more important than the others?
sarah hanlon associate editor the knot
Sarah Hanlon
sarah hanlon associate editor the knot
Sarah Hanlon
Associate Editor
  • Sarah is an Associate Digital Editor for The Knot, with special focuses in fashion, pop culture and wedding trends.
  • Before joining The Knot Worldwide, Sarah was a contributing writer for Bravo at NBC Universal.
  • Sarah has a degree in journalism and resides in New York City.
Updated Oct 22, 2021
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When you begin researching the perfect diamond engagement ring for your significant other, you might feel overwhelmed by the sheer volume of options on the market. A simple Google search will present you 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 "4C's." Most, if not all, shopping guides and jewelry websites include information about the 4C's. 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 4C's of diamonds are, it's helpful to know their origin, as well as why they matter. "The 4C's 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 4C's 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 4C's expert just because you're in the market for an engagement ring. While it's helpful to know the background of the 4C's 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 4C's," 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 4C's of diamonds in order of importance to help you feel confident in your engagement ring shopping experience. Before you're ready to commit to a sparkler, brush up on your diamond terminology so you know exactly what to expect when you start shopping.


If you had a hunch that there's a hierarchy to the 4C's, you're correct. The cut grade is the most important out of the group because it determines how brilliant the diamond is. "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 the brilliance, or what will make an engagement ring shine bright.


Next on the list of 4C's 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 C's, 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 are able to 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."


Clarity is the next most important factor of the 4C's 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 4C's 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."


Finally, carat refers to the weight of the diamond. As the diamond carat weight 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, 2.5 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 4C's, 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 4C's," 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 4C grade tends to be lower, the unique color and gradient is actually desirable for some.

Finding the perfect stone is all about following your own aesthetic while using the 4C's as a guide, rather than a rulebook. "Work within the 4C's 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 C's to pick the diamond for you."

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