In-Depth Round Brilliant Cut Diamond Buying Guide

The establishment of standardized grading practices and increased transparency in trading diamonds has led to round diamonds being recognized as commodities. As a result, their prices have become progressively competitive with narrow profit margins.

Retailers might use phrases like "heart & arrows" and "hearts on fire." However, the fundamental standards and techniques for cutting a round brilliant diamond remain relatively consistent. So long as buyers adhere to the prescribed proportions outlined below, they can adeptly identify a well-cut round diamond regardless of its brand name.

While we extensively discuss 4Cs and other critical quality factors concerning round diamonds in the sections below, we advise against compromising the quality of a round diamond's cut. Cutters employ various techniques to maximize yield from the original rough diamond, which might compromise the cut quality of the diamond. Our proportions chart below serves as an invaluable safeguard against such practices.

Round Cut Diamond Illustration by GIA. Copyrights: GIA

This cutting-edge 40X 360°HD technology can be immensely helpful in assessing cut quality. The innovative tool empowers buyers to evaluate the diamond's cut, color, and clarity, enabling them to pinpoint the location of inclusions and identify problematic black crystals and other flaws. Buyers can also access 360-degree 3D videos of thousands of diamonds through this platform.

Excellent vs. Super Ideal Proportions

The above chart is critical in discerning a super ideal cut diamond from an ideal or excellent cut counterpart, particularly when evaluating two diamonds both graded as excellent cut by GIA. Review the crown and pavilion angles and the girdle size to make an accurate distinction. Beyond the evident significance of depth and table, each of these factors contributes to the nuanced variations in cut quality.

For further insights, check our article on the importance of diamond cut. If budget constraints are factored in, there is leeway to consider a cut grade as low as "very good," provided certain conditions are met. A stone that isn't excessively deep—avoiding an overly small appearance—or excessively shallow—thus retaining brilliance and fire—can be a suitable compromise.

Here's an example of a very good cut diamond resembling an excellently cut one. Should buyers locate a diamond with comparable cut proportions, they shouldn't be overly concerned with it being graded as "excellent cut" by GIA. 

Color is considered as second most significant factor after cut when assessing a diamond's quality. White diamonds span from colorless (D-F) and near-colorless (G-J) to Z, encompassing shades ranging from faint to light yellow. While individuals with the means often favor colorless diamonds, G and H color diamonds offer remarkable choices. Opting for an H or I color diamond opens the possibility of utilizing faint to medium blue fluorescence, a trait that complements yellow hues and enhances the diamond's perceived whiteness.

Pro tip: When deciding between a VVS1 clarity H color diamond and a VS1 clarity G color diamond, the former (VS1 G) is a better choice, all other factors being equal. Exercise caution with strong blue fluorescence, particularly in D-G color round diamonds. This type of fluorescence can often detract from the overall appeal of high-color-grade diamonds.

The chart below serves as a valuable reference for a more detailed analysis of color in round cut diamonds based on carat weight.

Additional insights can be gleaned from our comprehensive diamond color scale and chart.

GIA's clarity grading scale for diamonds ranges from flawless (FL) to I3, with FL being the highest and I3 being the lowest. Ensuring minimal visible inclusions is pivotal to a diamond's overall aesthetic and brilliance. Assessing clarity, among the 4Cs, is a highly technical task.

Which types of inclusions are deemed acceptable, and which should be avoided?

In brief, avoid prominent black crystals and visible inclusions on a diamond's table. Furthermore, small inclusions uniformly dispersed across the stone are best—this characteristic ensures that inclusions remain indivisible to the naked eye. Lastly, verify that the diamond's clarity grade is not based on clouds.

Although not necessarily unfavorable inclusions, if a diamond's clarity grade hinges solely on clouds, the stone can take on a hazy, oily appearance devoid of the desired sparkle.

The chart below is a general guide for evaluating clarity in round diamonds:

Avoid a round diamond whose clarity grade is "based on clouds." These diamonds often lack the vibrant brilliance that characterizes a desirable gem. To ascertain whether a diamond's clarity grade is based on clouds, refer to the comment section within the GIA report, where it will indicate such findings. It is crucial to differentiate between the presence of clouds as inclusions, which typically pose no major concern, and a clarity grade based on clouds.

For further insights, refer to our diamond clarity guide.

In addition to the well-known 4Cs, buyers must be familiar with the following key aspects of a round cut diamond grading report or certificate, as highlighted in the image below.

Watch HD Video of this Diamond.

Measurements: This is important because it will inform the buyer of the diamond's surface size (how big the diamond will appear in millimeters).

Fluorescence: This should be considered as the 5th C. In this particular example, avoiding fluorescence is advisable since the color is F. However, medium blue fluorescence is not as problematic as strong blue fluorescence.

Comments: This section will display clarity-related factors and highlight whether a diamond is clarity-enhanced (through methods such as laser drilling or color enhancement, etc.). Additionally, watch for comments like "clarity grade based on clouds," which is a concerning sign in clarity grades of VS2 and below. The laser inscription of the report number on the girdle is above the comment section (an optional service for additional verification).

Proportions: This chart is crucial for assessing a diamond's cut. Specifically, pay attention to the table percentage (58% in the example—excellent), depth percentage (61.1%—excellent), crown angle (34° —excellent), pavilion angle (40.8° —excellent), girdle (medium, 3.5%—excellent), and culet (none—excellent).

Clarity Characteristics: This section will indicate the type of inclusions and their locations. It can assist buyers in avoiding diamonds with visible inclusions at the center. These details are also helpful for matching the report with the diamond, as these inclusions act as the diamond's birthmarks.

When striving to secure the finest diamond within a predetermined budget, navigating the intricate interplay of the 4Cs—carat weight, cut, clarity, and color—often poses a perplexing challenge for shoppers. To aid in addressing this quandary, consider the ensuing four scenarios prior to reaching a final verdict:

Investment Grade (Pinnacle of Quality and Rarity): In this range, discerning buyers accord paramount importance to diamonds of unblemished clarity (flawless/VVS) and colorless attributes (D-E). They seek diamonds with ideal proportions, backed by esteemed GIA and AGS certifications, and displaying no fluorescence. This category caters to those valuing the highest quality and rarity in their diamond selection.

High-Quality Large Diamonds (Optimal Value): Within this range, purchasers set their sights on diamonds with VS2/VS1 clarity and F/G color, coupled with negligible to faint fluorescence. The focal point is securing excellent value by obtaining a large diamond without compromising quality. Aiming for the most "bang for the buck" guides a buyer's pursuit.

Striking a Balance Between Size and Beauty: This scenario sees shoppers in pursuit of a large diamond while concurrently maintaining a threshold of quality. As an illustration, these buyers opt for a 1.5 carat diamond instead of a 1 carat variant. For instance, they may select a 1.5 carat round diamond featuring SI1 clarity, I color, medium blue fluorescence, and a very good cut rather than a 1 carat diamond with E VVS1 clarity. This approach harmonizes size and quality.

Maximizing Size on a Restricted Budget: Buyers with limited financial leeway emphasize the diamond's size and radiance, willingly accommodating some visible inclusions or a faint yellow tint if the stone remains affordable. Their focus may lead them to acquire a 2-3 carat L to M color diamond, characterized by inclusions such as non-black carbon crystals like feathers near the girdle. Augmented by strong blue fluorescence to enhance the color and provide a very good to excellent cut for optimal luminosity and dispersion, this approach places paramount importance on size. Under this scenario, we recommend that buyers compromise on color and buy a large diamond with an excellent cut and clarity grade.

Since 1750, round diamonds have undergone several changes, particularly in facet size and proportion variations. Ongoing modifications occur in the dimensions of a diamond's table, total depth, culet, crown, and the length of lower half facets. Nevertheless, diamonds from each era exhibit distinct and unique appearances.

Most buyers opt for round brilliant cut diamonds as they align with their contemporary aesthetic preferences. Round brilliant cut diamonds exhibit a closely-knit play of light and possess dark patterns due to their elongated lower half facets, a trait gemologists call "splintery."

Conversely, older cuts like the old European cut feature a small table, a prominent culet, a steep crown, and shorter lower half facets, resulting in a "blocky" or "checkerboard" pattern.

The Gemological Institute of America established the cut grading system specifically for unmodified round brilliant cut diamonds. To distinguish between the earlier iterations and the contemporary style, the term "unmodified round brilliant" refers to a symmetrical round cut diamond featuring 58 facets that are cut according to modern standards.

While GIA assigns five distinct cut grades (excellent, very good, good, fair, and poor) to assess the cut quality of modern round diamonds, AGS utilizes six cut grades by incorporating the "ideal cut" into the spectrum.

Key Differences between Old European vs. Modern Round Brilliant include:

Old European cut

• Lower half facet length: 60 percent or less
• Table size: 53 percent or less
• Crown angle: 40 percent or greater
• Culet size: slightly large

Round brilliant cut with 58 facets to be classified as a modern brilliant cut must adhere to the following criteria:

• Lower half length: 60 percent or less
• Culet size: medium or slightly larger
• Star length: 60 percent or less.

The diamond trade has undergone significant evolution in the past decade. The internet and the wealth of online information have empowered first-time buyers, eliminating the need to rely solely on local retailers for acquiring high-quality diamonds at reasonable prices. Instead, they can swiftly access diamond prices from various websites, enabling them to determine a competitive price range.

To illustrate, determining the cost of a 2 carat round cut diamond with VS1 clarity, G color, excellent cut, and no fluorescence graded by GIA or AGS is now relatively straightforward. Prospective buyers can explore prices on platforms like James Allen and Blue Nile to establish a reasonable value for the 2 carat diamond.

When buying round cut diamonds online, retailers should offer solid return options, lifetime warranties, and upgrade policies. A brand's reputation carries weight due to quality assurance considerations and the enduring support they offer. It might be worth investing an additional 5% for this assurance. Furthermore, opt for a seller offering complimentary repairs when a stone is dislodged from the mounting or when resizing the ring is necessary. For further insights, refer to our detailed article on the best places to buy diamonds.

Lastly, the popularity of lab-grown diamonds is on the rise, presenting viable budget-friendly alternatives to natural diamonds.

What characterizes a round cut diamond?

As previously mentioned, round diamonds stand as the most prevalent diamond shape. Due to their expansive surface area, they typically carry a higher price tag compared to fancy cut stones. Crafting a 1 carat round brilliant cut diamond necessitates a larger rough diamond than that required for a 1 carat princess cut diamond.

What are the optimal proportions for a round cut diamond?

Kindly refer to our proportion chart to determine the ideal round cut diamond proportions.

What should I emphasize when considering the 4Cs while purchasing a diamond?

The four scenarios we've discussed offer valuable insight into prioritizing the 4Cs when seeking a round diamond.

Which certifications hold the highest reliability for diamonds?

As previously indicated, GIA and AGS stand out as the best diamond grading labs globally.

How does fluorescence impact a diamond?

To comprehensively grasp the matter of fluorescence, please delve into our detailed article on the subject. This is a significant consideration, as its effect can be either adverse or advantageous, contingent on the diamond's color.

Which shape serves as a viable alternative to round diamonds?

An oval cut diamond presents itself as an exceptional substitute for round cut diamonds, owing to their inherent resemblances.

Is purchasing diamonds online a secure option?

Indeed, buying loose diamonds online is now notably secure. The establishment of a standardized grading system has considerably facilitated the process of procuring diamonds online.