When shopping for a diamond, cut is the factor that truly determines whether the stone will dazzle or disappoint. Carat weight, color, and clarity all matter—but without an exceptional cut, even the most flawless diamond can appear lifeless. To help buyers navigate this, Garry Holloway introduced the Holloway Cut Adviser (HCA) in 2001. More than two decades later, the HCA remains a well-known screening tool in the diamond world, valued for its ability to quickly filter out poorly cut stones.
Still, like any tool, it has its strengths and limitations. Understanding how the HCA works—and when to use it—can make the difference between choosing a diamond that sparkles endlessly and one that falls short.
What Exactly Is the HCA Tool?
The Holloway Cut Adviser is an online calculator designed specifically for round brilliant diamonds. It evaluates a diamond’s potential light performance based on a handful of key measurements from its lab report, including:
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Depth %
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Table %
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Crown angle
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Pavilion angle
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Culet size
By inputting these values, the HCA generates a score between 0 and 10. The lower the score, the greater the diamond’s potential for brilliance, fire, and scintillation. As a general rule:
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0–2: Excellent—worth strong consideration.
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2–4: Very Good—may still perform well, especially at the right price.
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4–6: Good—better for budget-conscious buyers.
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6–8: Fair—performance will likely be disappointing.
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8–10: Poor—avoid, as brilliance will be severely compromised.
It’s worth noting that a score of 0 is essentially unattainable, and most top-performing diamonds fall between 0.5 and 1.5.
How the HCA Helps (and Where It Falls Short)
The value of the HCA lies in its simplicity. In seconds, you can rule out diamonds with proportion combinations that are unlikely to deliver excellent sparkle. But its simplicity is also its greatest limitation:
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Two-Dimensional Model: The HCA evaluates basic proportions, not the actual three-dimensional facet alignment. This means it cannot account for symmetry issues that may affect brilliance.
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No Facet Detail: Star facets, upper girdle facets, and other subtle features are ignored, even though they influence light performance.
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No Optical Analysis: Advanced systems such as AGS’s Light Performance grading or tools like ASET and IdealScope can show how light actually behaves inside a diamond. The HCA, by contrast, provides only a calculated estimate.
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Rounding and Averages: Because the tool relies on averages from lab reports, it may not reflect the precise nuances of the diamond you’re evaluating.
When Should You Use the HCA?
Think of the HCA as a first line of defense. If you’re browsing diamonds with a GIA Excellent cut grade, the HCA can help weed out stones that look good on paper but are proportioned in ways that compromise performance.
However, it should never be the final step in your decision. If a diamond scores under 2, the next step should be to request images, ASET or IdealScope scans, and of course, rely on a trusted gemological lab report.
The Bottom Line
The Holloway Cut Adviser is best understood as a filter, not a guarantee. It’s an excellent way to eliminate obvious underperformers, but it doesn’t replace a detailed optical analysis or the trained eye of a jeweler. When used alongside advanced evaluation tools and professional grading, the HCA remains a helpful ally in the search for a diamond that will truly sparkle for a lifetime.
At Dinah Vela, we believe every diamond tells a story—and brilliance should never be compromised. That’s why we combine traditional expertise with modern diagnostic tools, ensuring every diamond we offer exceeds expectations in beauty and performance.