The 4Cs of Diamonds: A Comprehensive Guide + Buying Tips

The science behind diamonds...

Diamonds are incredibly durable, and their sparkle is bewitching. For many, they’re the signature stone of marriage👰🏻, and they remain the most popular stone for engagement rings. But, how do you know when you have found a quality diamond?

Let’s discuss the four categories used to grade diamonds—commonly known as the “4Cs”—and common practices to implement when purchasing diamonds to help you buy smart.

A Gemologist Inspecting the 4Cs of a Diamond With a Loupe

The origin of the 4Cs

When were the 4Cs invented? What are they for?

The 4Cs were created by Robert M. Shipley in the 1940’s. He branded “the 4Cs” as a mnemonic aide to help students of gemology remember the four main characteristics used to grade a diamond.

Once the GIA was established and Richard T. Liddicoat came to power, he used Shipley’s initial 4Cs to create standardized grading scales and criteria for optimizing the gemstone grading process. Liddicoat and his successors revolutionized the diamond industry by developing the D–Z color scale in 1953 and producing all of the scientific measures used to grade diamonds objectively.

Today, the 4Cs are used to grade a diamond and provide a precise value for each gemstone. Scientific measurements are impartial, which allows gemologists to provide a fair, efficient rating for each diamond. Although the science behind grading is complex, the scales used are easy for the average buyer to understand. As such, the 4Cs allow buyers to have a better understanding of diamonds and compare values accordingly.⚖️

What is the GIA?

Logo of the Gemological Institute of America (GIA)

Shipley believed the American jewelry industry should be streamlined to provide customers, gemologists, and retailers with a better understanding of gemstones and their qualities. As such, he established the Gemological Institute of America (GIA) in 1931 to train and certify jewelry professionals.

Today, the GIA is the most well known non-profit source of geological knowledge globally. A scientific authority that is committed to protecting diamond buyers, the GIA enforces high standards of integrity and professionalism through its certification processes and educational programs.

How are the diamond 4Cs used by other groups?

Another group that utilizes the 4Cs is the American Gem Society (AGS). Shipley also established the AGS to provide a guild for gem professionals to share knowledge and expertise. Both groups use the 4Cs to educate people about diamond quality, and while their ratings may sometimes be a little different, they tend to agree in most situations.

💡The AGS and GIA use nearly identical scales, but the AGS grades diamond cuts on a scale from 0–10. The AGS uses a 0–10 scale for clarity and color too, and the ratings match up with the GIA’s word-based scale. Several other groups have their own renditions of the 4Cs as well, including the IGI, EGL, and more!

📝What are the 4Cs of diamonds?

The 4Cs of diamonds are cut, color, clarity, and carat weight. These four criteria interact with one another to create the brilliant sparkle of diamonds. Additionally, diamond anatomy plays a large role in the 4Cs, as differences in diamond proportions and measurements can affect their grade. Before you dig into the 4Cs, make sure you familiarize yourself with diamond anatomy to better understand the physical characteristics that affect these grading criteria.

We’ve broken down each of the 4Cs below, but take a look at our diamond 4Cs chart for a brief overview:

CutHow well a gem cutter has shaped the facets of a diamond to allow light to reflect, refract, and disperse through the stone
ColorThe measurement of a diamond’s hue, with colorless diamonds being more valuable than those with a yellow or brown tint
ClarityAn inspection of the “inclusions” and “blemishes” of a diamond and how much they affect its sparkle
Carat WeightThe weight of a diamond, expressed in whole carats with partial carats up to the hundredths place (i.e. 2.34 or 1.05)


A diamond’s cut is arguably the most important factor in its brilliance.🌟 The shape of a diamond is independent of its cut. Shape refers to the exterior outline of the diamond: is it shaped like a rectangle? A triangle? A heart?  In contrast, the diamond’s cut measures the level of precision used by the gem cutter to create a well-proportioned, symmetrical, and polished stone.

Diamonds are graded by their ability to reflect, refract, and disperse light. The sides or “facets” of the diamond interact with light and play a huge role in how much a gem glitters. Without a proper cut, even a diamond graded well for color and clarity can lack the characteristic twinkle.

Well-Cut Shiny Diamond Insolated on Black Background

👉🏻The GIA grades diamond cuts on a specific scale: Poor, Fair, Good, Very Good, and Excellent. How a diamond’s cut will grade depends on multiple factors: proportions, girdle thickness, polish, and facet symmetry. Additionally, these criteria play into three major areas of interest in grading:

FireThe ability of light to scatter within the diamond and create a rainbow of colored light
BrightnessThe white light reflected from a diamond both internally and externally
ScintillationThe amount of white flashes and bright light sparkling across the diamond’s surface in relation to dark areas or spots

Whether a diamond boasts 22, 2, or .2 carats, the care and craftsmanship put into its cut will make it shine above the rest!


Color—or lack thereof—is crucial to quality, as diamonds are naturally colorless and any color may signify an impurity or quality concern.

To judge a diamond’s color, gemologists view it under controlled lighting in very specific lab settings to ensure they give the proper grade. “Masterstones” or diamonds used as the baseline for rating, are also utilized to provide an accurate grade.

The GIA’s diamond color grades range from D to Z. Diamonds ranging from D to F are considered “Colorless”, and G–J are classified as “Near Colorless”. However, once a diamond surpasses J, color differences become increasingly discernible with the naked eye, progressing all the way to Z.

Diamond Color Gradings: D, H, N and Z
Image: GIA
GIA Diamond Color Scale From D to Z

As stones reach the further end of the scale, they take on a yellow or brownish hue. Lower quality diamonds may also have chemical impurities or structural defects, causing them to lack the luster and durability desired.

Colored Diamonds

Bonus Info

Colored diamonds, also known as “fancy” diamonds, are vibrant variations that are stunning in their own way.

In fact, colored diamonds come in a wide range of colors, including pink, blue, yellow, green, brown,  purple, and more.🌈 These colors can occur naturally, but labs can also create colored diamonds to suit all tastes. While natural colored diamonds often develop in lighter hues, lab-created colors are saturated and sometimes don’t even look like diamonds at all!

White diamonds may have the 4Cs, but colored diamonds have their own grading criteria. They somewhat mirror those characteristics used in the 4Cs, but with a few twists:

Colored Diamonds

Grading ScaleDifferences From White Diamonds
CutThe cut must emphasize the stone's color, but it does not need to be symmetrical, balanced, etc.
ColorGraders measure the most saturated areas of color, focusing on tone, hue, and saturation
ClarityInclusions are not a problem if they do not affect the color or durability of the diamond
Carat WeightLarger stones with saturated color are rarer and more valuable


Most diamonds are imperfect, and clarity measures their natural makeup which includes flaws known as “blemishes” and “inclusions”. Blemishes are marks on the exterior surface of the diamond, whereas inclusions are internal flaws.

To verify clarity, a gemologist must examine the diamond to decide how many—if any—flaws a diamond has, their location and size, and how they affect the scintillation and appearance of the stone overall. Diamonds can receive one of the following ranks depending on their flaws:

Clarity Scale GradeDefinition
IFInternally Flawless
VVS1Very Very Slightly Included (1)
VVS2Very Very Slightly Included (2)
VS1Very Slightly Included (1)
VS2Very Slightly Included (2)
SI1Slightly Included (1)
SI2Slightly Included (2)
I1Included (1)
I2Included (2)
I3Included (3)

Diamond Clarity Flaw - Inclusion: Cloud
Inclusion: Cloud

Diamond Clarity Flaw - Blemish: Polish Lines
Blemish: Polish Lines

Outside of blemishes and inclusions, another factor that can influence clarity is cut. For instance, inclusions are much more noticeable in larger stones or those with fewer facets, such as an emerald cut diamond. By maximizing carat weight or choosing a cut with large surfaces, you may actually be choosing a diamond with a lower clarity than a smaller stone!

Carat Weight

Carat weight is the weight of the whole diamond—not its size/surface area—and a carat is 200 milligrams. Diamond measurements are expressed in whole carats with partial carats up to the hundredths place, such as 2.04, 1.03, and .25. This allows graders to properly categorize different sized diamonds with precision, which can impact their overall value.

Typically, retailers price diamonds per carat. Additionally, a diamond’s shape and other qualities can affect how much you will pay. For instance, with a 1 carat round brilliant cut diamond, you may expect to pay $2,500–$18,000 for a stone of mid-range quality.

💡While weight is a factor in price and value, it’s really a combination of the 4Cs that determines this. If two diamonds are of similar cut, color, and clarity, then the larger of the two will typically be pricier. But, even a .5 carat stone can outrank larger diamonds of lesser quality if its other factors are stronger.

Key facts you should know about the 4Cs

Diamond grading is a complex process, and it can be hard to decide what you value most when choosing a diamond. Overall, the 4Cs all play into a diamond’s brilliance, and you should make an educated decision based on your understanding of color, cut, clarity, and carat weight.

⚠️Here are some key facts to remember when shopping for a diamond:

Carat Weight

As mentioned before, some people believe size matters when buying diamonds. If you agree, consider figuring out your ideal diamond size and then looking at stones about .10–.20 smaller than that. As previously mentioned, generally diamonds are priced per carat, so even the slightest change in weight can mean a higher price. Small weight changes are nearly unrecognizable in diamonds, so you may be able to get a gem that still looks large for less!

Clarity and Color

Judging a diamond’s inclusions or color can be difficult. Even with a jewelry loupe, you may not be able to detect any defects that affect a diamond’s shine, and the color is often barely discernible among gems that are one or two grades off from one another. If you don’t notice an inclusion or feel it doesn’t detract from a diamond’s beauty, then don’t be afraid to look at lower clarity or color diamonds that may suit your needs.


If you value a diamond’s sparkle above all else, consider prioritizing cut. While all of the Cs are important, the cut is what gives a diamond its fire. Try a diamond with a slightly lower clarity and color and a quality cut to see if it meets your expectations.😎

When in doubt: Consult a jeweler

While you may choose not to purchase your diamond from a jewelry store, it can be helpful to have a jeweler you know and trust to help you. Jewelers have years of training that can help you find the right diamond for your needs. They can discern minute differences among stones and help you get a good quality gem for your money. Consider looking for a certified gemologist near you!

Recommended practices when buying diamonds

Still unsure of how to find the right diamond for your needs? Consider these additional practices when shopping for diamonds:

Which of the 4Cs is most important?

While all 4Cs are important when seeking a balanced diamond, a high-quality cut is paramount to getting that brilliant sparkle. Cut can be considered the most important C, but we recommend finding a happy medium with an excellent cut and good clarity and color for the ultimate fire. However, keep in mind this could mean sacrificing a bit of carat weight!

The 5th C: the Diamond Certificate

Always make sure you get a copy of the unofficial 5th C: the Diamond Certificate. A Diamond Certificate—which has different names depending on the group who graded the stone—is an unbiased report from a grading authority that details your stone’s specifics, including the 4Cs, dimensions, and more.

Many retailers, such as Blue Nile, allow you to view and download a copy of the report before you purchase the stone. James Allen even allows buyers to search diamonds by their preferred grading authority, such as the GIA, AGS, or IGI.

Some organizations, such as the IGI, have slightly more lax criteria when it comes to the 4Cs, so we recommend either sticking with the high standards of the GIA and AGS or doing your own extensive research on these groups before buying!

👉🏻From 4Cs to 7Cs: Other possibilities to consider

The 4Cs are a great tool for gauging the quality of loose diamonds. However, if you’re looking to create a unique piece and place your chosen stone in a band, necklace, or other settings, here are 3 more Cs to consider:

Center Stone

The center stone of your piece drives its value, as it is the main focal point of the setting. While accent stones can add value, their qualities are typically less important than those of the main diamond. Finding the right center stone is key, as it’s going to dictate price, style, and grading. 📝If you’re looking to save money on your center stone, consider a halo setting that surrounds a smaller, high-quality center diamond with accent stones to add size.


Consider creating your own piece with a trusted jeweler. You can purchase your diamond independently and add any setting that fits your stone’s shape. You can even buy accent diamonds separately to add flair to your piece. A custom piece is also a great way to add a personal spin on any engagement ring!


If you’re looking for something unique, consider stepping outside the bounds of white diamonds. Fancy colored diamonds, sapphires, rubies, and emeralds make great centerpieces for jewelry, and other semi-precious stones would look beautiful as well. Or, switch up your metal setting to something less commercial, such as rose gold, palladium, or titanium. Make your piece an extension of yourself through customization and creativity.

Consult a professional when buying online

If you plan to buy your diamond online, you may want to talk to an expert first. James Allen and other respectable online jewelers offer diamond consulting services as you shop! Just look for the “Talk to an Expert” button or related link to speak with a professional who can give you a better understanding of how to shop for your ideal diamond. Having a diamond expert to help you search can mean the difference between hours and months of searching!

Diamond Ring in a Jewelry Box

Put your 4Cs education to good use

Diamond buying is tricky, but with a good jeweler on your side, you can make informed decisions about your purchase.

At the end of the day, it often comes down to what people prize most: quality or quantity. While you may find a larger diamond that seems like a good deal, it may not have the excellent clarity, cut, and color of a smaller stone. 💎Finding the right balance of these qualities that fits your budget is the toughest part of purchasing the right diamond.

Regardless of a diamond’s retail value, the true value lies in the memories you make with it. Whether it’s an engagement ring, a gift for graduation, or a little something to tell him you love him, may your diamonds always sparkle and bring you joy.❤️

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