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 a complete brilliant-cut facet pattern.
  • Make sure that you are familiar with both square and rectangular radiant cut diamonds. See the image above as it illustrates perfect ratios for both types.
  • We recommend a length-to-width ratio of 1-1.05 for square and 1.16-1.3 for rectangular, depending on how elongated you want the stone to look.
  • While analyzing the cut, look for a table of 57-69% and depth of 58-70%. Review the chart below for precise numbers and other important factors related to cut.
  • Buy a radiant cut diamond that is graded by either GIA or AGS.
  • In terms of prioritizing the 4Cs, if you want a premium radiant cut in the investment grade range, go for this (example 1). If you want to maximize both quality and carat weight, a stone like this would be good to consider (example 2). If you do not mind compromising slightly on quality to maximize carat weight, consider a stone in this range (example 3). Finally, one way to maximize 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 our 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 allow it to emanate a tremendous amount of shine. A radiant cut diamond is a vibrant and exuberant square/rectangular stone and has a complete brilliant-cut facet pattern applied to its crown and pavilion. It is also an excellent reflector of light, having served as an alternative to the emerald cut diamond since its invention. Since the 1970s, radiant cut diamond has been a popular choice. All credits go to Henry Grossbard, the mastermind behind the shape of radiant cut diamond.

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

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 regarded as a classic cut for both square and rectangular shapes of the radiant cut diamond, though personal preference could override it. 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. The nice bridge between the cushion and princess cut makes it look beautiful when 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 price difference. 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 one that meets your standards in terms of clarity. Each of our customers has a unique standard for clarity and color. Some want a flawless diamond, while others are perfectly comfortable with a slight inclusion if it is not easily noticeable. 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 too have beautiful and elegant looks to them as well.

    What is the best alternative to radiant cut diamonds?

    Radiant cut diamonds are alternatives to emerald cut diamonds that have more of a step-cut and fewer facets. If you want deep large facets, emerald cut diamonds would be the way to go. But if you want 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 a 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.) 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 price reflects the difference.) 

    Square vs rectangular radiant cut

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