If you had performed a little research about buying engagement rings, you probably have heard about a myriad of technical terms and jargon. The “four C’s”, table and depth %s, proportions, shapes and certificates probably things you might already have came across.

However, most of us cannot do anything meaningful with these data apart from comparing them to tables of “recommended proportions”. Fortunately, there is a simple system developed by Garry Holloway that can help you gleam deeper into a round diamond’s proportions.

The Holloway Cut Advisor, or as it is most commonly known, the “HCA” simplifies the process of judging the potential quality and appeal of a standard round brilliant cut. Let us take a look at how it works and why it could be a handy tool especially if you intend to purchase an engagement ring “blind”.

A Brief History of the Holloway Cut Advisor

The founder of HCA, Garry Holloway, is not a newcomer to the business and had joined in the industry since the early ’70s. Besides being a partner with one of the largest jewelry forum, he is also actively involved in diamond cut and research development with scientists from Russia and India.

After an intense study of how the various diamond proportions and angles interact with each other, he developed the HCA software. This program enabled the layman to key in variables found in the grading report and makes an instant prediction on the diamond’s visual appeal and performance.

how to use holloway cut adviser

The free simulation software can be found here => Holloway Cut Adviser

Upon entering data into the HCA software, it will return a score ranging from 0 to 10 (a numerical figure below 2.0 is desired).

0-2 Excellent
2-4 Very Good
4-6 Good
6-8 Fair
8-10 Poor

An Overview of the Software’s Strengths

The HCA provides an assessment of a diamond’s potential light return, scintillation, spread and fire. It attempts to assess features that are closer to the actual visual appearance of a diamond and the grade is determined based on 4 factors:


Light Return


Combined, these 4 factors result in the Total Visual Performance of a diamond. A HCA score of less than 2 denotes a diamond that has desirable qualities and reflects light in an optimal way.

Note: The Holloway Cut Advisor will never replace a physical appraisal carried out by experts or the data an ASET/Idealscope provides, but it can definitely be considered a great helping tool you can use on your own, for free.

Using the HCA as a Rejection Tool

Here’s an example of how you can use it to weed out seemingly similar looking stones based on grading certifications. For comparison’s sake, I chose 2 round diamonds from James Allen which are graded by GIA as Excellent cuts and plugged their cut proportions into the tool.

Did you know that JamesAllen.com’s video technology allows you to inspect diamonds upclose with a 360° magnified view? Click here to see every little detail of a diamond like never before.

details of actual proportions from gia reports

I would instantly reject the diamond on the right based on the HCA findings.

How to Use the Holloway Cut Advisor Tool



As you can see, the HCA tool is a very fast and handy tool to help you weed out stones that fall short of having great optics. In order to confirm your findings, you should also view the idealscope data to find out more details.

comparison of 2 idealscope images for round brilliant cuts

The diamond on the left shows a good performing round brilliant diamond under the Idealscope and this corresponds to the 1.2 HCA score that was received by the diamond. On the right, the image exhibits a leaky stone with light loss through the table facet as shown by the pale ring.

Even the Software Has its Weaknesses – What You Need Know

On a first glance, the HCA tool might appear to be the cleverest application created for the diamond shopper. However, a good score on the HCA tool doesn’t necessary indicate a diamond with best light performance/precision due to a variety of factors. The first reason behind having discrepancies is that the HCA tool only utilizes the measurements of 17 out of a total of 57 facets for its analysis.

To put things into perspective, the HCA score will not reveal whether the scintillation pattern of the stone has a pin fire or a broader flash characteristic. Besides relying on averaged readings, the HCA tool fails to take into account the girdle thickness variations, polish and symmetry ratings. Combine as a whole, these factors form a complex relationship which are all part and parcel of delivering light performance.

The next shortfall of the HCA is that it is only applicable for round brilliant cut diamonds. Fancy shapes or modified round cuts cannot be subjected to an analysis because the algorithm doesn’t work for them.

There are a lot of other factors that can influence the appeal and the value of a diamond. For example, a diamond’s HCA score will not reflect potential problems caused by a low clarity grade. Issues that may cause the stone to take up a hazy appearance or have adverse impacts on brilliance cannot be predicted by a computer algorithm.

Conclusion About the Usage And Results of the HCA

Taking everything into account, we can say that a HCA score is only useful to a certain degree. The tool provides quick results based on a limited set of data inputs. The Holloway Cut Advisor is not meant as a tool for selection but rather, a tool to reject poorly proportioned stones.

Once you had weeded out the poor performers which score more than 2.0 on the HCA, you should apply other optical examination tools like the ASET or Idealscope in your final selection process. This will help you cherry pick the most brilliant stone from the remainder of diamonds with a HCA score of less than 2.0.

On this note, where are the best places to get your diamonds where you can get access to ASET/Idealscope tools? Continue reading to find out more…

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  1. Avatar
    July 28, 2013 at 3:06 pm

    I don’t really get the part on scintillation about pinfire or broad flash scintillation. When I entered in values for pavilion and crown angles into the HCA software, it returns an Excellent rating for the scintillation and a 1.8 for Total Visual Performance.

    Should I try to get a diamond that has less than 1.0 in score so that it performs better?

  2. Avatar
    Paul Gian-
    July 29, 2013 at 1:37 am

    Hi Jocelyn,

    A low score of 0.6 or 0.4 on the HCA doesn’t necessarily mean it will look better in real life as compared to another with 1.8. You should look at its this way. A diamond with less than 2.0 on the HCA passes the first round of quality checks.

    Take note, 2 diamonds with the same exact set of proportions will have the same HCA score. However, these 2 diamond may look completely different in reality. Thereafter, you need to get more data on the particular stone you are interested in.

    With regards to the broad flash or pinfire characteristics, this is largely depended on the lower girdle facet length. Typically, a length of more than 85% will result in a splintery look while ranges between 75% to 80% tend to display chunkier flashes of light.

    Hope this helps!


  3. Avatar
    November 5, 2014 at 6:24 am

    Hi Paul,

    Can I conclude that any diamond with more than HCA 2.0 is not worth to considering?

  4. Avatar
    Paul Gian-
    November 5, 2014 at 6:49 am

    To be on the safe side of choosing a well-cut diamond, I would say yes.

    However, if you have idealscope/ASET images and they indicate a nicely cut diamond, then the HCA score doesn’t really matter. There do exist well-cut diamonds with HCA scores between 2.0 – 3.0.

  5. Avatar
    November 5, 2014 at 9:19 am

    If that’s the case, have you seen any diamond that have HCA 4-5 but very good cut under the scope?

  6. Avatar
    Paul Gian-
    November 5, 2014 at 9:24 am

    No. None that I can recall.

  7. Avatar
    September 10, 2017 at 11:18 pm

    what do you think of this diamond? it seems to fit all the criteria

  8. Avatar
    Paul Gian-
    September 11, 2017 at 8:54 am

    I don’t see any details or urls in your comment. You might had accidentally clicked submit before you completed your comment.

  9. Avatar
    March 11, 2018 at 12:08 pm

    Hi Paul,
    just for your information:
    Your link to the HCA software on Gary Holloway’s website http://www.idealscope.com has been deleted for some months. He shifted it to https://www.pricescope.com/tools/hca. For private users it is free of charge. Professional users pay for it now.

    Cheers, Torsten

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