Diamond Proportions: Modern Round Brilliant Cuts

1. Descriptive Proportions Chart

Descriptions are general. Read these usage notes.
Combinations on this chart range from predicted AGS 0 (Ideal) Light Performance to AGS 2 (Very Good).
Use the Holloway Cut Advisor (HCA) to verify predicted light return. The best HCA score is Excellent.
Request Ideal-Scope or ASET images for diamonds you are considering and post them on our forum for help.

Click chart to enlarge.

Warning: The chart above does not account for factors which may interfere with light transmission like undisclosed haze, clouds, etc. Read our page on Diamond Clarity for this information, along with the useful PriceScope eye-clean definition.

Want help? Post information about any diamond you’re considering on our Diamond Discussion Forum for free guidance from dozens of experienced jewelry lovers and experts.


2. Member Recommended

Members of the PriceScope community have historically recommend a narrow range of “foolproof” proportions which will receive top marks in the strictest cut grading systems, including HCA Excellent, AGS Ideal and GIA Excellent.

Largely contained in the “All Around” category above, diamonds with these proportions are predicted to have balanced brightness, fire and contrast.

Member Recommended Proportions*

Crown Angle: 34 – 35 °
Pavilion Angle: 40.6 – 40.9 °
Lower Halves: 75 – 80 %

Table: 54 – 57 %
Total Depth: 60 – 62.5 %
Girdle: Thin – Medium – Slightly-Thick

* Notes when using GIA reports, as their laboratory rounds some numbers up or down:

  • When GIA pavilion angle is 40.8 ° any crown angle above is okay
  • When GIA pavilion angle is 40.6 ° lean toward a crown angle 34.5 – 35.0 °
  • When GIA pavilion angle is 41.0 ° lean toward a crown angle of 34.0-34.5 °


Where to Find Proportions Data

Proportions Map


Learn more about brightness, leakage, contrast and scintillation on our page Diamond Performance Explained.

Get fast answers to any question: Ask our community of unbiased independent helpers.

Ready to find your diamond?