The 4Cs of Diamonds: Diamond Quality Guide

Last updated May 6, 2024

Buying a diamond engagement ring can be a confusing and even stressful experience. The idea of proposing is nerve-wracking enough without having to worry about whether you’ve overpaid for a mediocre diamond!

Here’s where knowing the “4Cs” of diamond quality – cut, color, clarity, and carat weight – can help you to make an informed selection. After reading this guide, you’ll have a firm understanding of the 4Cs and how to apply them when evaluating diamonds.

How Is Diamond Quality Assessed?

In the mid-20th century, the Gemological Institute of America (GIA) created the 4Cs of diamonds and the International Diamond Grading System. This led to gemstone laboratories offering diamond grading reports based on the 4Cs, providing diamond customers with an impartial overview of a diamond’s quality.

GIA is the major and most trusted independent provider of reports for gem quality diamonds. Other labs also provide diamond grading services, but their reporting is generally considered less robust and consistent than that offered by GIA.

Reading a diamond’s report is a critical part of the buying process. Skip this step, and you’re taking the vendor’s word for it that the diamond is real and of the quality the vendor claims.

In the following sections, we’ll look at each of the 4Cs and how to recognize their grades in a diamond report. Report reference images are taken from this sample report provided by GIA.

1. Diamond Cut

A diamond cut grading scale showing Excellent to Poor cut diamonds.
Diamond Cut Grade Scale

Did you know that diamonds don’t sparkle when they come out of the ground? It takes the work of a skilled diamond cutter to cut diamonds into faceted gemstones, thereby unleashing their signature brilliance, fire, and scintillation.

A diamond’s cut refers to its proportions, symmetry, polish, and overall appearance – that is, the quality of the diamond cutter’s work. The better the cut, the more the diamond’s facets interact with light, and the greater its beauty.

Cut is considered the most important of the 4Cs, simply because cut quality can make the most significant impact on a diamond’s appearance.

Let’s say that you’re holding two diamonds of equal carat weight, color, and clarity. Because the first diamond has a high quality cut, it sparkles brightly. But the second diamond is cut badly, which makes its sparkle subdued and lifeless.

TL;DR: Cut is the most important of the Cs of diamonds, so you should prioritize it when making your selection.

Diamond Cut Grades

A report showing diamond cuts grading information.

Under the Grading Results heading of a GIA diamond report, a diamond’s overall cut grade is given one of five possible scores:

  • Excellent
  • Very Good
  • Good
  • Fair
  • Poor

Under Additional Grading Information, you can also see two separate scores for polish and symmetry.

When all three are graded Excellent, the diamond may be (informally) referred to as having a “Triple Excellent” cut.

Good to know: Only round brilliant diamond shapes receive GIA cut grades. Cut grading systems for other diamond shapes have yet to be developed.


Excellent is the best diamond cut grade overall. Although the most expensive, Excellent cuts are worth it for their higher levels of brilliance and scintillation.

However, not all Excellent cuts are created equal. Just because a diamond is Excellent or even Triple Excellent graded, doesn’t necessarily mean it’s the best of the best. It certainly doesn’t mean you should buy it based on its cut grade alone.

The smart approach is to use a diamond’s cut grade to narrow your choices to Triple Excellent cuts. From there, you can apply further elimination tests to come to the best possible diamond.

We go into detail about this process in our dedicated article about diamond cut.

Very Good

Very Good cuts interact with light reasonably well and can be good picks for necklaces, earrings, and similar types of diamond jewelry. But for a purchase as big and meaningful as an engagement ring, it’s safer to go with an Excellent cut.

Good, Fair, and Poor

Good cut diamonds are the “average” diamonds placing in the middle of the grade scale. They can have some visual appeal, but lack any “wow” factor.

Continuing down the scale, Fair cuts are below average, and Poor cuts are abysmal and should be avoided at all costs.

TL;DR: Limit your shortlist to Triple Excellent cuts only. Cut is the one 4C where you shouldn’t compromise.

See also: Diamond Cut: How to Pick the Best and Sparkliest

2. Diamond Color

A diamond color scale showing colorless to light color diamonds.
Diamond Color Grade Scale

When thinking about diamond color, the one that naturally comes to mind is clear icy white – in other words, a lack of color.

But the vast majority of gem quality diamonds aren’t completely colorless. Most carry a warm tint, caused by impurities that were present during their geological formation.

The less color tint a white diamond has, the higher its value. Truly colorless diamonds can command truly spectacular prices to match.

The good news is, you don’t have to spend big on this 4C grade to get a beautiful diamond. This is because diamonds that aren’t colorless can still look white, depending on factors such as:

  • Diamond shape: Round brilliant diamonds are good at concealing color impurities in a diamond, whereas other shapes such as the cushion cut tend to show color more.
  • Cool metal ring setting: White metals like platinum or white gold can make slightly color-tinted diamonds look whiter than they are, because the diamond will reflect some of the metal’s own whiteness. But white metals can also make more strongly tinted diamonds appear yellower by contrast.
  • Warm metal ring setting: Yellow gold and rose gold settings can make colorless and slightly tinted diamonds appear less white by contrast, and more strongly tinted diamonds look whiter by disguising the tint with their own warm color.

When evaluating a diamond’s color, the key factor is how it actually looks when mounted in your chosen ring setting. The diamond’s color grade on paper is less important than its real-world appearance.

TL;DR: Colorless diamonds are very expensive. Save money by choosing a lower color graded diamond that looks white to the naked eye.

Diamond Color Grades

A GIA report showing a diamond's color grade.

A white diamond’s color grade is assigned on a scale that begins at D and ends at Z.

Depending on its letter grade, a diamond is placed into one of five color categories:

  • Colorless
  • Near Colorless
  • Faint
  • Very Light
  • Light

For our purposes, we’ll only be looking at Colorless, Near Colorless, and Faint diamonds, which is the range between D-M. Very Light and Light diamonds in the N-Z range are noticeably discolored, making them unsuitable for engagement rings.

The D-Z scale doesn’t apply to fancy colored diamonds, which are graded on different criteria.

Colorless (D-F)

Diamonds in the D-F color range have no visible tint, either to the eye or under 10x magnification. Colorless diamonds are the rarest and most highly priced type of white diamond.

However, spending a premium on a D-F grade diamond is unnecessary, as only experts using professional tools would be able to tell its real color grade. To everyone else, a Colorless diamond looks exactly the same as a Near Colorless diamond.

Near Colorless (G-J)

Diamonds that are graded G-J appear colorless to the eye when mounted in a ring setting and viewed face up. If viewed from different angles as a loose stone, or viewed under magnification, slight traces of color are visible.

G-J diamonds offer the best combination of beauty, quality, and value.

For a round diamond set in a white metal, you generally shouldn’t go lower than a J color grade. Otherwise, the white metal setting may appear whiter than the diamond itself.

Faint (K-M)

K-M graded diamonds have a faint yellow or brown tint that may be noticeable to the naked eye. This can depend on factors like lighting quality, viewing angle and distance, and the shape of the stone itself.

While they’re more affordable than Colorless and Near Colorless diamonds, the slight tint of K-M diamonds can make them unattractive when set in white gold or platinum jewelry.

However, a Faint color diamond can be the perfect match for a yellow gold or rose gold setting. A Colorless or Near Colorless stone won’t look colorless in a warm metal setting anyway, since the diamond will reflect some of the metal’s own color.

By the same token, a yellow or rose gold setting can help a Faint color diamond look whiter than it really is, because people will expect to see some of the metal’s color reflected in it.

TL;DR: For a traditional round cut diamond set in a white metal, pick a Near Colorless (G-J) diamond. For a yellow or rose gold setting, go for a Faint (K-M) diamond.

See also: Diamond Color Scale: Getting the Best Value for Money

3. Diamond Clarity

A chart showing different diamond clarity grades from Flawless to Included.
Diamond Clarity Grade Scale

Diamond clarity is graded on the visibility of a diamond’s physical imperfections under 10x magnification. The fewer and less prominent these imperfections, the higher the diamond’s clarity grade.

Imperfections in diamonds come in two categories:

  • Inclusions: Internal flaws formed within a diamond as a result of geological pressures. Some common inclusions are fractures, fissures, clouds, crystals, and dark spots.
  • Blemishes: Surface-level flaws caused by damage sustained during the diamond cutting or mounting process. Nicks, chips, and scratches are some typical blemishes.

A diamond with inclusions or blemishes can still appear flawless if its imperfections aren’t visible without magnification, or are located in less noticeable areas.

For instance, a diamond’s report may reveal an inclusion deep inside the stone, or a small chip on one of its sides. But if you can’t actually see that imperfection with your own eyes, then the diamond is still a good buy – and at a cheaper price than if it had a higher clarity grade.

TL;DR: Though most diamonds have flaws, not all flaws are visible. Your goal should be to find a diamond that’s eye-clean – meaning it appears flawless to the naked eye.

Diamond Clarity Grades

A report showing a diamond's graded clarity, clarity plot, and types of imperfections.

A diamond’s clarity grade is located under the Grading Results heading of a GIA diamond report.

Diamonds are further classified into one of six clarity categories:

  • Flawless
  • Internally Flawless
  • Very Very Slightly Included
  • Very Slightly Included
  • Slightly Included
  • Included

Under the Clarity Characteristics heading, you can also see the types and locations of a diamond’s inclusions and blemishes.

Flawless and Internally Flawless (FL and IF)

A Flawless (FL grade) diamond has no inclusions or blemishes visible under 10x magnification. An Internally Flawless (IF grade) diamond has no inclusions but does have visible blemishes under 10x magnification.

FL and IF diamonds are extremely rare and expensive. But to the naked eye, they appear no different to many lower clarity diamonds that are more affordable.

Unless you have a psychological or symbolic reason to want a perfectly clear diamond, there’s no need buy in the FL-IF range. Your budget would be better spent on getting a higher cut grade or a bigger diamond.

Very Very Slightly Included (VVS1 and VVS2)

The Very Very Slightly Included range includes VVS1 and VVS2 diamonds. They contain tiny inclusions that are difficult to spot under 10x magnification, even by a trained professional.

VVS1 and VVS2 diamonds are almost always eye-clean, while being less expensive than FL and IF diamonds.

Very Slightly Included (VS1 and VS2)

VS1 and VS2 diamonds are Very Slightly Included, with small inclusions that are somewhat difficult to find under 10x magnification.

Most VS1 and VS2 diamonds are eye-clean. This is a good value grade range to shop in.

Slightly Included (SI1 and SI2)

SI1 and SI2 diamonds are Slightly Included with noticeable inclusions that are easy to see under 10x magnification, and can also be visible to the naked eye.

Only some SI1 and SI2 diamonds are eye-clean, but the ones that are can be great deals if you can find them.

Included (I1, I2, and I3)

Diamonds in the Included range have inclusions and blemishes that are obvious under 10x magnification.

With vary rare exceptions, these diamonds aren’t eye-clean and should be avoided.

TL;DR: Look for eye-clean diamonds within the VS1 to SI2 ranges. So long as it’s eye-clean, your diamond’s actual clarity grade doesn’t really matter.

See also: Diamond Clarity Chart: What’s the Best Clarity Grade?

4. Diamond Carat Weight

A chart showing different diamond shapes with carat weight numbers and approximate sizes.
Diamond Carat Weight to Size Scale for the three most popular diamond shapes (round, princess, and oval)

Diamond weight is measured using the diamond carat system. A carat equals 0.2 grams (or 200 milligrams) worth of diamond. Which means a 1 carat diamond weighs 0.2 grams, a 2 carat diamond weighs 0.4 grams, and so on.

As diamond size increases with carat weight, a higher carat diamond looks more impressive than a lower carat one, all other things being equal.

The trouble is, all other things are usually not equal. In fact, the other 4Cs of diamond quality tend to decrease as carat weight increases.

The main reasons for this are:

  • Cut quality is often sacrificed in favor of diamond weight. Heavier diamonds fetch higher prices. But giving a diamond a superior quality cut requires cutting away more of its mass, thereby reducing its total weight. This incentivizes cutters to retain as much diamond weight (and profit) as possible – usually at the expense of cut quality.
  • Color tint and inclusions are more prominent in higher carat diamonds. When comparing diamonds in the same color grade, larger stones are more likely to show color. Similarly, inclusions tend to be more visible in higher carat diamonds.

To strike the ideal balance between carat and everything else, keep this simple rule in mind:

Don’t spend more on carat if it means spending less on cut.

If you want a bigger stone, compromise on color and clarity instead. A top-tier cut will hide many shortcomings of color and clarity anyway.

But with a badly cut diamond, all of its shortcomings are noticeable – and their prominence increases as the diamond’s carat weight gets higher.

TL;DR: Resist the temptation to spend less on cut in order to spend more on carat. You’ll only end up with a big but dull and cheap-looking diamond.

Diamond Carats and Sizes

A GIA report showing the carat weight grade for a 1.01 carat stone.

There’s no right or wrong diamond carat weight number. Although around 1 carat is the most common choice for an engagement ring in the United States, this 4C is entirely subjective and down to personal preference.

Saying that, you should be aware that different diamond shapes show different face-up sizes, even if their carat weights are the same. For example, a well-cut 1 carat round brilliant diamond measures around 6.4mm in diameter, while a 1 carat princess cut weight measures only around 5.5mm.

Therefore, if getting the biggest-looking diamond for your budget is the priority, you may want to limit your selection to diamond shapes that look large for their carat weight. These include round, oval, pear, emerald, marquise, and trillion cut diamonds.

Also keep in mind that diamond size doesn’t increase proportionally with carat weight – that is, a 2 carat diamond isn’t twice as big as a 1 carat diamond. For instance, a 2 carat round diamond measures 8.1mm across, which is only a 26.6% increase in face-up size from a 1 carat round diamond.

TL;DR: A higher carat weight doesn’t necessarily translate to a huge-looking diamond. Pay attention to a diamond’s shape and measurements when selecting for size.

See also: Diamond Carat Size Chart & Buying Guide and The Top 12 Most Popular Diamond Shapes

Recap: How to Apply the 4Cs of Diamonds

A man sliding a diamond engagement ring onto a woman's finger.
Man proposing with a beautiful diamond ring

In a nutshell, you can think of it this way:

Cut and carat weight are the diamond 4Cs that you want. You want the best cut diamond possible in the carat weight that you like and can afford.

Conversely, color and clarity are the 4Cs that you tolerate. You don’t want a perfectly colorless, perfectly clear diamond – that would be a colossal waste of money!

Instead, you tolerate the fact that your diamond won’t have perfect color and clarity grades, and pick one that looks colorless and clear when mounted in its ring setting.

To summarize, our recommended 4Cs for a beautiful yet affordable diamond are:

  • Cut: Triple Excellent (for round diamonds).
  • Color: Between G to M, depending on diamond shape, carat weight, and ring setting.
  • Clarity: Between VS1 to SI2, so long as it’s eye-clean.
  • Carat: According to your preference and budget.

Now that you’re up to speed on the basics of the diamond 4Cs, it’s time to take your knowledge to the next level by gaining a comprehensive understanding of the most important 4C – diamond cut.