Buyer's Guide to Radiant Cut Diamond & Quality Insights

Buyer's Guide to Radiant Cut Diamond & Quality Insights

Buyer's Guide to Radiant Cut Diamond & Quality Insights

Posted by Sharif Khan on 8th Jan 2021

radiant cut ratio

Key Takeaways:

  • In terms of fire and brilliance, you cannot go wrong with radiant cut diamonds. The shape has 70 facets and complete brilliant-cut facet pattern. 
  • Make sure you are familiar with both square and rectangular radiant cut diamonds. See the image above as it illustrates perfect ratios for both types.
  • A length-to-width ratio of 1-1.05 for square and 1.16-1.3 for rectangular is recommended, depending how elongated you want the stone to look. 
  • While analyzing the cut, look for total table of 57-69% and depth of 58-70%. Review the chart below for precise numbers and other important cut related factors. 
  • Buy a radiant cut diamond that is graded by either GIA or AGS.
  • In terms of prioritizing the 4Cs, go for a diamond like this if you want a premium radiant cut in the investment grade range (example 1). If you want to maximize on both quality and carat weight, a stone like this would be good to consider (example 2). If you don't mind compromising slightly on quality in order to maximize on carat weight, a stone in this range would be good to consider (example 3). Finally, one way to maximize on cut, clarity and carat weight is to compromise on the color. In this case, something like this might be a way to go (example 4). 
  • Here is a list of out top websites for diamonds and engagement rings to consider. 

radiant cut proportions

Overview Radiant Cut:

Radiant Cut diamond is one of our favorite diamond shapes. The 70 facets in a radiant cut diamond allows it to emanate a tremendous amount of shine. Radiant cut diamond is a vibrant and exuberant square/rectangular diamond that has complete brilliant-cut facet pattern applied to its crown and pavilion. Radiant cut diamond is also an excellent reflector of light - this is why it served as an alternative to the  emerald cut diamond when it was invented. Since 1970’s, radiant cut diamond has been a popular choice, and credit goes to Henry Grossbard – the mastermind behind the shape of radiant cut diamond.

Tools like's 3D 360 Degree 40X Magnified Videos can be very helpful in assessing how change in proportions and length to width ratios affect the appearance of an a radiant cut diamond. Try to use the outlined proportions below and play with their search filter to get a good sense of what might be a good option for you.  

Analyzing Radiant Cut Diamond:

Depth %
  • Poor/Far: <52 or >80 / 52-80
  • Good: 57-59 / 71-74.5
  • Very Good: 58.8-70/67-70.1
  • Excellent: 61.3-67
  • Table %
  • Poor/Fair: <50 or >80/50-52.5 or 75.5-80
  • Good: 53-57/74
  • Very Good: 58-61/71
  • Excellent: 62-70
  • Culet
  • Poor/Fair: Large/Very Large
  • Good: Medium
  • Very Good: None/Very Small
  • Excellent: None
  • Girdle
  • Poor/Fair: Ex. Thin – Ex. Thick
  • Good: Very thin - thick
  • Very Good: Very thin - slightly thick
  • Excellent: Very thin - slightly thick
  • Length to Width Ratio for Square Cut
  • Poor/Fair: >1.09 /1.07-1.09
  • Good: 1.05-1.06
  • Very Good: 1.00-1.04
  • Excellent: 1.00-1.04
  • Length to Width Ratio for Rectangular Cut
  • Poor/Fair: <1.08 or >1.41/1.07-1.08
  • Good: 1.09-1.13/1.37-1.41
  • Very Good: 1.14-1.20/1.32-1.36
  • Excellent: 1.20-1.31
  • James Allen

    The chart above serves as a general guideline when evaluating the cut of a radiant diamond. The length to width ratio of 1.00-1.04/1.20-1.31 is considered the classic cut for both square and rectangular shape of radiant cut diamond, but the personal preference could override that. Consider the radiant cut diamond if you appreciate the sophistication of emerald diamond and the fire of a round diamond; it would be a perfect combination of a round and an emerald diamond in terms of fire and sophistication. You can also obtain a perfect combination between the cushion and princess cut if you look at its cropped corner square shape. That nice bridge between the cushion and princess cut makes it look beautiful set with either round or square corners.

    Evaluating Radiant Cut Color:

    Just like evaluating the color in other diamond shapes, color in a radiant cut diamond is critical. The higher the color grade, the better. In our experience, many buyers prefer the warmer colors over the colorless colors given the difference in price. In the color spectrum, the warmer colors refer to the near colorless range of G-I color diamonds while the colorless colors refer to D-F color diamonds. The price premium for a lower color grade radiant cut diamond would be significantly lower. 

    For more detailed information on the color of cushion cut diamond, use the table below.

    < 0.50 Carat
  • Poor/Far: >M/ L-M
  • Good: I-K
  • Very Good: G-I
  • Excellent: D-G
  • 0.51 – 1.0 Carat
  • Poor/Fair: J-K / >L
  • Good: I
  • Very Good: H
  • Excellent: D-G
  • 1.0 – 2.0 Carat
  • Poor/Fair: J-K / >I
  • Good: H-I
  • Very Good: G
  • Excellent: D-F
  • >2.0 Carat
  • Poor/Fair: I-K / >I
  • Good: I
  • Very Good: G-H
  • Excellent: D-F
  • Fluorescence
  • Poor/Fair: Very Strong
  • Good: Strong 
  • Very Good: Medium Blue/Faint/None
  • Excellent: None
  • Choosing Radiant Cut Clarity:

    Choosing the kind of clarity is subjective in a radiant cut diamond. Choose a radiant cut diamond that meets your standards in terms of clarity. Each of our customers has a unique standard for clarity and color. Some of our customers want a flawless diamond while others are perfectly comfortable with a slight inclusion as long as it is not easily noticed. In our experience, considering any clarity above SI2 (GIA standards) would be perfectly fine!

    < 0.50 Carat
  • Poor/Far: I2 / >I2
  • Good: I1-I2
  • Very Good: SI1-SI2
  • Excellent: FL-VS2
  • 0.51 – 1.0 Carat
  • Poor/Fair: I2 / >I2
  • Good: SI2
  • Very Good: SI1-SI2
  • Excellent: FL-VS2
  • 1.0 – 2.0 Carat
  • Poor/Fair: SI2-I1 / >I1
  • Good: SI1-SI2
  • Very Good: WS2-VS2
  • Excellent: FL-VS1
  • >2.0 Carat
  • Poor/Fair: >SI2
  • Good: SI1-SI2
  • Very Good: VS1-SI1
  • Excellent: FL-WS2
  • Suggested carat weight, cut, color and clarity of Radiant Cut Diamond for people with budget constraints

    Excellent Choice

    • At least 1.0 carats in Weight
    • Very Good to Excellent Polish and Symmetry
    • G or above in color
    • SI1 or above in clarity
    • No Florescence
    • Length/width ratios: 1.0-1.04 for a square or 1.20-1.35 for a rectangular shape

    Very Good Choice

    • At least 0.90 carats in Weight
    • Good to Excellent Polish and Symmetry
    • H or above in Color
    • SI1 or above in Clarity
    • None, faint or medium blue florescence
    • Length/width ratios: 1.0-1.04 for a square or 1.20-1.35 for a rectangular shape

    Good Choice

    • At least 0.80 Carats in Weight
    • Good to Very Good Polish and Symmetry
    • I or above in Color
    • SI1 or above in Clarity
    • None, faint or medium blue florescence
    • Length/width ratios: 1.0-1.04 for a square or 1.20-1.35 for a rectangular shape.

    Frequently Asked Questions About Radiant Cut Diamonds:

    Which one is better, the square or rectangular radiant cut diamond?

    It entirely depends on your budget, we have seen both options in the market. While the elongated ones look bigger, the square radiant cuts have beautiful elegant to look to them as well. 

    What are best alternative to radiant cut diamonds?

    Radiant cut diamonds are alternatives to emerald cut diamonds which has more of a step-cut and fewer facets. If you want a deep large facets, emerald cut diamonds would be the way to go. If you want lots of sparkle and radiance, radiant cut would be the choice. 

    Why are radiant cut diamonds cheaper than round cut diamonds?

    They are not necessarily cheaper than round diamonds. Round diamonds have large surface size and therefore a one carat round diamond would require a bigger rough diamond than it would for a radiant cut (for example the average surface size of a 1 carat round diamond is about 6.4mm while it would be in the 5.5mm range for a square radiant cut). So in reality, while they are both the same in carat weight, the cutter had to sacrifice a bigger rough diamond to get a 1 carat round diamond than s/he had to for a radiant cut (the difference is reflected in price). 

    Square vs rectangular radiant cut

    Be sure to check out our loose diamond page to compare actual prices of different companies.