---
title: "Diamond anatomy and proportions"
description: "Diamond anatomy: the parts of a round brilliant and every proportion on a grading report, explained with our free Cut Grading Tool."
url: https://digitalgemology.com/learn/diamond-anatomy
image: https://digitalgemology.com/img/learn/XY6EXlrCHf4.jpg?v=802e6b12
---

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[Learn](https://digitalgemology.com/learn)

# Diamond anatomy and proportions

Nine lessons · five videos · read them in any order

These pages name every part of a round brilliant and explain every proportion on a grading report: table, crown, pavilion, star and lower half lengths, girdle and culet. Each page uses our free Cut Grading Tool, 3D Gemstone Simulator or Hearts & Arrows Scope, so you can change one proportion and see what it does to the light and the grade. The last page puts it all together and decodes a stone from its numbers.

New here? Start with [Pavilion angle and pavilion depth: how a diamond keeps the light in](https://digitalgemology.com/learn/diamond-anatomy/diamond-pavilion-angle).

1. 1 · Video
  ## [The parts of a diamond: crown, girdle and pavilion](https://digitalgemology.com/learn/diamond-anatomy/parts-of-a-diamond)
  Crown, girdle and pavilion, the 57 facets of a round brilliant by name, and what each part does with light.
2. 2 · Article
  ## [Diamond measurements explained: diameter, depth and percentages](https://digitalgemology.com/learn/diamond-anatomy/diamond-measurements-explained)
  Read the measurements line, work out the total depth, and see how crown height, girdle and pavilion depth add up.
3. 3 · Video
  ## [Diamond table percentage: what table size does to the light](https://digitalgemology.com/learn/diamond-anatomy/diamond-table-percentage)
  How table size is measured, what a bigger table does to the crown and the grade, and why bigger is not brighter.
4. 4 · Video
  ## [Crown angle and crown height in a round diamond](https://digitalgemology.com/learn/diamond-anatomy/diamond-crown-angle)
  What the crown angle does with light, how it sets the crown height, and how a steeper pavilion can rescue a shallow crown.
5. 5 · Animated explainer
  ## [Pavilion angle and pavilion depth: how a diamond keeps the light in](https://digitalgemology.com/learn/diamond-anatomy/diamond-pavilion-angle)
  How the pavilion keeps the light in, what too shallow and too steep look like, and the narrow Excellent window.
6. 6 · Video
  ## [Star length and lower half length in a round brilliant](https://digitalgemology.com/learn/diamond-anatomy/star-length-and-lower-half-length)
  What star and lower half lengths measure, how they shape the pattern and the hearts, and what painting and digging cost.
7. 7 · Article
  ## [Diamond girdle thickness: thin, medium, thick and what it costs you](https://digitalgemology.com/learn/diamond-anatomy/diamond-girdle-thickness)
  How a girdle is described, the trade between durability and hidden weight, and the thicknesses that keep a round Excellent.
8. 8 · Article
  ## [The diamond culet: none, pointed or large](https://digitalgemology.com/learn/diamond-anatomy/diamond-culet)
  What the culet is for, its eight sizes, how a large one shows face up, and how much it can cost a grade.
9. 9 · Article
  ## [How to read diamond proportions: decode a stone from its numbers](https://digitalgemology.com/learn/diamond-anatomy/how-to-read-diamond-proportions)
  A six-step routine to read a full set of proportions, predict the cut grade and find the one number that limits it.

## Quick quiz

Every lesson ends with a few questions. Want more? [The Anatomy of a diamond quiz](https://digitalgemology.com/skool/quiz/anatomy-of-a-diamond) covers the whole topic, with the answer and the reason after each question.

## Cuts in this topic

We sell the files of these cuts: 3D models and cutting files, with a personal-use license.

- [T73 Round Brilliant Cut](https://digitalgemology.com/cuts/t73-round-brilliant): 3D files and cutting files, €9.99 each
- [T57 Round Brilliant Cut](https://digitalgemology.com/cuts/t57-round-brilliant): 3D files and cutting files, €9.99 each
- [T105 Round Brilliant Cut](https://digitalgemology.com/cuts/t105-round-brilliant): 3D files and cutting files, €9.99 each
- [Mazarin Cut](https://digitalgemology.com/cuts/mazarin): 3D files and cutting files, €9.99 each

[All topics](https://digitalgemology.com/learn)