Round Cut Diamonds In-Depth Guide

Round Cut Diamonds In-Depth Guide

Round Cut Diamonds In-Depth Guide

Posted by Sharif Khan on 7th May 2020

Round Diamond 4Cs and Proportions

ideal round cut chart

Table of Contents:

  • Key Highlights
  • Overview & Important Background
  • Cut Quality & Ideal Proportions
  • How to Prioritize the 4Cs
  • Color in Round Cut Diamonds
  • Round Cut Clarity Details 
  • Additional Background and Q&A

Bottom Line Recommendation:

  1. Round Cut Diamond is the most popular diamond shape, and because of its brilliance, it's often recognized as a symbol of the diamond trade itself.  
  2. In terms of cut, a total depth of 59-62.5% and a total table of 53%-58.5% is preferred in round brilliant cut diamonds. See the chart below for detailed information. 
  3. Fluorescence is often a negative factor, but it can be helpful in some cases. See more below. 
  4. GIA and AGS are the best grading labs, make sure you buy a diamond that is graded by one of these two labs. 
  5. In terms of color, while D to F are top color grades, we also recommend G color. H and I are amazing budget color options as well. 
  6. Flawless to VSS/VS1 clarity ranges are great, but VS2 is also safe. SI1/SI2 are good budget options. Review the clarity characteristics and inclusions location in SI1/SI2 carefully to make sure the stone is eye-clean. 
  7. If you don't have a budget problem, look for a round diamond that has specs like this one (option 1) if you have a good budget and want a nice quality large stone, specs like these are what we would recommend (option 2), if you want a big stone within a tight budget but also don't want an ugly looking diamond, buy something this (option 3), and if you have a very tight budget and want a big diamond, you may compromise on color and maximize on clarity and cut (option 4).  

James Allen


Round Brilliant Cut Diamonds make up roughly 70-80% of all polished diamonds traded around the world. Due to progress in research and the development of a standard method for grading diamonds, round diamonds have become more like a commodity and their prices are increasingly becoming standard with very small margins for markups by retailers.

The Gemological Institute of America (GIA) Introduced the standard cut grading system for "unmodified" round brilliant cut diamonds in 2005. According to GIA, for a round diamond to qualify as an unmodified round brilliant cut diamond, it has to have 58 facets and cut according to modern standards. American Gems Society (AGS) on the other hand uses a proportion-based grading system.

The diamond trade has evolved significantly over the last decade. Thanks to the internet and GIA, you are no longer at the mercy of local retailers to buy diamonds at a 150-200% markup. You can easily review diamond prices online on 4-5 different websites and get a good sense of what a competitive price might be for a given range, say a Round Cut 2ct., VS1, G Color, Excellent Cut with no Fluorescence graded by GIA or AGS.

Analyzing the Cut:

In terms of cut, while many marketers call their round cut diamonds with taglines like "heart & arrows", "hearts on fire", "a cut above" etc., the benchmarks and method for cutting a round brilliant cut diamond is more or less the same, and as long as you follow the guidelines below, you should be able to determine what a well-cut round diamond is regardless of its brand name.

Tip: James Allen also has the best cutting-edge 40X 360°HD technology that you should use as a tool for comparing the cut of a diamond based on the proportions below as well as for assessing diamond clarity to locate the location of inclusions (also to assess if they are bad black crystals). It doesn't cost anything to use their filter and explore thousands of diamonds in a 3D 360 degree view. 

Depth %
  • Poor/Fair: <56/>65%
  • Good: 57.6-58/63.4-64.5
  • Very Good: 58-59/62.8-63.3
  • Excellent: 59-62.6
  • Table %
  • Poor/Fair:<50/>68.5>
  • Good:51-52/62-64
  • Very Good: 51-52/59-62
  • Excellent:53-58.5
  • Culet
  • Poor/Fair: Medium
  • Good: Small
  • Very Good: None/Very Small
  • Excellent: None
  • Crown Angle
  • Poor/Fair:<28.5/>38.5
  • Good: 30-32/36-38
  • Very Good: 32-34/35-36
  • Excellent: 34-35
  • Pavilion Angle 
  • Poor/Fair: <39/>46
  • Good: 41-42/44-45.3
  • Very Good: 41.3-42.6/43.3-43.8
  • Excellent: 40-41.2
  • Girdle
  • Poor/Fair: Ex. Thin – Ex. Thick
  • Good: Very thin - thick
  • Very Good: Very thin - slightly thick
  • Excellent: Thin - slightly thick
  • 58 Facets Round Cut Diamond Illustration by GIA. Copyrights: GIA 

    If you get stuck on the cut issue, please review our article on is the diamond cut important? In this article, we basically explain that while the cut is absolutely critical, if budget is an issue, you can go as low as very good or good cut as long as you are ensuring that the stone is not either too deeply cut (in which case it would look very small) or is overly shallow (in which case it won't have fire and brilliance). 

    Here is an example of a very good cut diamond that is as good as an excellent cut diamond and if you find something like this, don't worry about why it is not graded "excellent." Sometimes it just comes down to the opinion of the gemologist grading it. 

    round cut diamond very good cut

    Excellent vs Super Ideal Cut:

    The chart above is critical in determining a super ideal cut diamond over an ideal or excellent cut diamond while comparing two diamonds that have obtained an excellent cut from GIA. Please pay attention to the crown angle, pavilion angle, and girdle size. These three make the difference in addition to the quality of the depth and table.

    In-depth Video Explanation on How to Analyze the cut of a Round Cut Diamond:

    In this video, Sharif provides in-depth explanation into the different aspects of round cut diamonds. It is a lengthy video, but well worth your time as analyzing the cut of a round diamond can be a challenging task. 

    Prioritizing 4Cs:

    One of the hardest questions for shoppers often is how to compare round diamonds and what C of the 4Cs they should compromise on in order to get the best diamond within budget - Carat Weight, Cut, Clarity, and Color. Please watch the video below where we explain four scenarios which would help you in deciding what approach is best for you within your budget.

    These Four Scenarios Include:

    1 – What we consider Investment Grade (High Quality and Rare):

    Basically Flawless, Colorless D, Super Ideal Proportions, No Fluorescence, GIA graded diamonds will be the highest reference point and the driving force behind the decision-making of the buyer in each carat range.

    2 – What We consider Investment Grade and Best Option (High Quality and High Circulation)...

    In this range, we look at what is high circulation and high quality. Basically, the shopper looks for VS2/VS1 and G/H color diamonds with no to faint/medium blue fluorescence and excellent to very good cut grades. The shopper’s goal is to get the biggest bang for their buck, but also do not want to overly compromise on quality.

    3 – Getting the largest, yet best-looking diamond (What we call a balanced approach):

    This is where shoppers look for the biggest stone but still care about the quality of the diamond to a degree. They still want the stone to sparkle. So they would go for as low as H/I color diamond, compromise a little on clarity and fluorescence, but aim for a 1.5 carat diamond instead of a 1 carat for the same money. So If I was the shopper, my goal would be to get a 1.5 carat round diamond with SI1 clarity, I color, medium/strong blue fluorescence, very good cut with good proportions instead of going for an E 1ct. VVS1 Excellent cut with no fluorescence. I would still be maintaining some level of quality and aiming for a larger stone.

    4 – Getting the largest possible within a tight and low budget:

    In this scenario, the shopper mainly cares about the big size of the diamond that still shines and doesn't mind some visible inclusions or the yellow tint of the diamond. So they would go for a J/K color diamond, 2-3 Carat, SI2 range with inclusions being non-black carbon crystals like feathers towards the girdle, strong blue fluorescence to aid the color, and very good to excellent cut for optimal brilliance and fire. 

    Analyzing the color issue:

    Color is the second most important C after the cut while assessing round cut diamonds. Diamond color ranges from Colorless (D-F), Near Colorless (G-J), and the rest to Z are considered faint, light and faint yellow. While colorless diamonds are always best for people that can afford it, we also love G/H color diamonds. If you buy H or I color diamonds, faint of medium blue fluorescence would be helpful as it is a complementary color to blue and can help make your diamond look whiter. 

    Hint: If you come to a point where you have to either compromise between either VVS1 clarity H color or VS1 clarity G color, go for the VS1 G - all other factors being equal.

    Diamond color scale

    Analyzing the issue of Clarity:

    GIA grades diamond clarity from Flawless to Included 3 - FL to I3. Not only do people want to avoid visible inclusions in their diamonds, but it can also affect the overall brilliance and fire of a diamond. Therefore, make sure you are familiar with the settle importance of diamond clarity. 

    Clarity is one of the most technical Cs in a diamond. What types of inclusions are good and bad? What should you avoid? 

    Avoid big black crystals. Make sure the inclusions are not on the table of the stone in the center. Make sure they are small and spread out inclusions which will make it less likely to be seen with the naked eye. Finally, make sure that  the clarity grade is not based on clouds. Clouds are not bad inclusions, but if a stone's clarity grade is based on clouds it means the stone is full of them, and therefore it is hazy and oily and won't have any sparkle at all. 

    GIA Diamond Clarity Chart

    Important Points to Consider While Shopping for a Diamond:

    Even though the trade has improved significantly and it is relatively safe now to buy diamonds online, it is still a good idea to shop a reputable store just to be on the safe side. Make sure they offer you a solid return policy, lifetime warranty, and lifetime upgrade policy. Two sites that stand out to us include James Allen (for GIA graded diamonds) and (for Ideal AGS graded diamonds). Moreover, we would highly recommend that you buy a stone that is graded by either GIA or AGS.

    The reputation of a brand is important because all sorts of games are being played to sell inferior stones at a higher price. Pay 5% more, but buy at a place who will support you when a stone falls off your mounting or when you need to resize your ring (some of the new sites might not be around next year, but they will happily promise you a life-time warranty). 

    Suggested Options for Buyers with Budget Constraints:

    Excellent Choice:

    • At least 1.0 carats in Weight
    • Very Good or Excellent Cut with Very Good to Excellent Polish and Symmetry
    • G or above in color
    • SI1 or above in clarity
    • No/faint Florescence

    Very Good Choice:

    • At least 0.90 carats in Weight
    • Very Good Cut with Good to Excellent Polish and Symmetry and very good proportions. 
    • H or above in Color
    • SI2 or above in Clarity
    • No, faint or medium blue Florescence

    Good Choice:

    • At least 0.80 Carats in Weight
    • Good Cut with Good to Very Good Polish and Symmetry with good proportions. 
    • I or above in Color
    • SI2 or above in Clarity
    • None, faint or medium blue florescence

    Additional Background:

    In today’s marketplace, roughly 75-80% of all diamonds sold are round shaped. There are varieties of round cut diamonds available, but the most common ones have 57 to 58 facets. Since 1750, diamonds have witnessed a plethora of changes especially in variation the of facet size and proportions. New styles and changes are made especially in the diamond’s table size, total depth, culet size, crown height, and length of the lower half facets.

    Nonetheless, diamonds from every era have had unique and quite discrete appearances. Some of the conspicuous changes in diamonds include larger table facets, smaller culets, and longer lower half facets.

    Most consumers tend to choose round brilliant cut diamonds because it meets their modern concepts of aesthetics. Round brilliant cut diamonds have a tighter mosaic of light and dark patterns with longer lower half facets which gemologists categorize as “splintery” pattern.

    The older cuts like the old European cut have a small table, large culet, steep crown, and shorter lower half facets, which gives them a “blocky” or “checkerboard” pattern. In spite of their beauty, it is quite difficult to judge them against modern round brilliant cut diamonds due to differences in their proportions.

    The Gemological Institute of America introduced the cut grading system for unmodified round brilliant cut diamonds. In order to distinguish between the older style brilliant cut diamonds, the term “unmodified round brilliant” is used for a symmetrical round cut diamond which has 58 facets and is cut according to the modern standards.

    GIA uses five cut grades including Excellent, Very Good, Good, Fair, and Poor to determine the cut of a round cut diamond. AGS on the other hand uses six cut grades by adding "ideal cut" to the equilibrium.

    Here are some of the key differences between old European and modern round brilliant cut diamonds:

    According to GIA, old European cuts have the following specifications:

    1. Lower half facet length: less than or equal to 60 percent
    2. Table size: less than or equal to 53 percent
    3. Crown angle: greater than or equal to 40 percent
    4. Culet size: slightly large or larger

    While the 58—facet round brilliant cuts have to meet the following requirements to be called modern brilliant cuts:

    1. Lower half length: less than or equal to 60 percent
    2. Culet size: medium or larger
    3. Star length: less than or equal to 60 percent.

    European Vs Modern Round Cut

    The image above is a good side by side comparison of the two different round diamond cuts. Notice the European cut has a small table, large culet, and short lower-half facets, while the round brilliant cut has a larger table, smaller culet, and much longer lower-half facets.

    Here an illustration of an AGS Ideal Round Brilliant Cut Diamond:

    AGS Ideal Round Cut Diamond

    To conclude, here is a summary of the top questions we have tried to answer in this article:

    What is a round shape diamond? 

    As stated earlier, round diamonds are most popular among diamond shapes. Please note that because round diamonds generally have a large surface size, they are generally more expansive than fancy cut stones. You would need a bigger rough diamond to cut it into a 1 carat round brilliant cut diamond than say you would to cut it into a princess cut diamond. It is for this reason only why round-shape diamonds are generally pricier than non-round diamonds. 

    What are the ideal proportions for a round cut diamond? 

    Please carefully review and follow our diamond proportion chart and guide for reference while evaluating the cut of round cut diamonds. 

    What should I prioritize in terms of the 4Cs while buying a diamond?

    The above four scenarios that we explained should be very helpful in terms of prioritizing the 4Cs while budgeting for a round diamond.  

    What are reliable diamond certifications? 

    As stated above, GIA and AGS are the best diamond labs in the world. GIA is the king. 

    How does fluorescence affect a diamond? 

    Please carefully review our guide on diamond fluorescence. It is an important topic to be familiar with as it can be both a negative and positive factor depending on the color of the stone. 

    What is a good alternative shape to round diamonds?

    In our opinion, an oval cut diamond would be a good alternative to round cut diamonds. Oval cuts are becoming very popular lately.  

    Is it safe to buy diamonds online?

    Yes, the diamond trade has evolved significantly over the years. Thanks to GIA, now we also have a standard grading system which makes buying a diamond online very easy. Just make sure you are buying a diamond that is graded by either GIA or AGS from a reliable website online.

    Round Cut Diamond