The Ultimate Guide to the 4Cs of Diamonds: Finding Your Perfect Engagement Ring
When it comes to diamonds, you have to deal with all those intimidating grading parameters. The 4Cs of diamonds explain why two stones might look similar, but their prices can be worlds apart.
Don’t worry—after this guide, you’ll know how to spot the real value! Whether you’re choosing a diamond for a classic engagement ring or a pair of unique handcrafted vintage earrings, understanding the 4Cs of diamonds is key.
Understanding the 4Cs of Diamonds
1. Carat in the 4Cs of Diamonds
Carat is the unit of weight for a diamond. One carat equals 200 milligrams and is divided into 100 points. So, when you hear “30 points” or “50 points,” it refers to a diamond weighing 0.3ct or 0.5ct.
Diamonds of the same carat can appear to have different sizes depending on the cut. Interestingly, a square-cut diamond of the same carat can appear about 15% larger than a round-cut one.
The Price Factor: Everyone knows that the bigger the diamond, the higher the price. But the price doesn’t increase linearly—it skyrockets at key weight thresholds.
Tip: Diamonds over 1 carat often hold investment value, while those over 0.3ct typically have reliable resale value.
2. Color in the 4Cs of Diamonds
Diamond color grading classifies diamonds by how much of a yellowish tint they have. The scale ranges from D (colorless) to Z (light yellow). Diamonds below grade Z are typically used for industrial purposes.
| Color Category | Grades |
| Colorless | D, E, F |
| Near Colorless | G, H, I, J |
| Faint Yellow | K, L, M |
| Very Light Yellow | N, O, P, Q, R |
| Light Yellow | S, T, U, V, W, X, Y, Z |
A yellowish tint can significantly affect a white diamond’s value—the yellower it is, the lower the value. However, a strong, saturated yellow is considered a Fancy Yellow Diamond, a type of colored diamond where the deeper the color, the more valuable it becomes.
To learn more about colored diamonds, read our PeonyJewels blog post: The Art and Science of Fancy Colored Diamonds: How Design Enhances Color and Value.
Tips:
- For colorless diamonds, an F-color is often more cost-effective than a D-color diamond of the same grade, with minimal visual difference.
- Even small accent stones will look whiter and more brilliant when using high-color diamonds rather than ordinary white ones.
3. Clarity in the 4Cs of Diamonds
Clarity refers to the presence of internal (inclusions) and external (blemishes) imperfections. A trained professional uses a 10x magnification loupe to grade it. Grades range from Flawless (FL) to Included (I), with VVS, VS, and SI in between.
Diamond Clarity Grading Table
| Clarity Grade | Description | Subdivisions |
| IF (Internally Flawless) | No internal flaws; no inclusions visible under 10× magnification. | None |
| VVS (Very Very Slightly Included) | Extremely minor inclusions. | VVS1, VVS2 |
| VS (Very Slightly Included) | Minor inclusions. | VS1, VS2 |
| SI (Slightly Included) | Noticeable inclusions. | SI1, SI2 |
| I (Included) | Inclusions visible to the naked eye. | I1, I2, I3 |
Diamonds often contain tiny imperfections like pinpoints, clouds, or feathers. These inclusions can block or deflect light, affecting a diamond’s brilliance and color tone.
To dive deeper into the specific types of flaws that affect clarity, read our PeonyJewels blog post: Diamond Cracks and Inclusions: Feather Inclusions and Cleavage Explained.
Tips:
- Inclusions in SI1-grade diamonds and above are typically not visible to the naked eye and don’t affect sparkle. Focus more on Cut quality.
- Visual Distinction (SI2 vs. I1): If a flaw is clearly visible to the naked eye without magnification, the grade is usually I1 or lower. If a flaw is difficult but possible to spot, it’s often SI2.
4. Cut: The Diamond’s Fire and Brilliance
Why Diamond Cut Matters Most
The Cut, often considered the most crucial of the 4Cs, directly dictates a diamond’s brilliance and light performance. An ideal cut reflects nearly all light that enters the stone, maximizing its vibrant fire and sparkle.
GIA Cut grades for Round Brilliant diamonds range from Excellent (highest) to Fair. Only about 3% of all diamonds achieve the coveted Excellent cut grade. Cutters often balance cut quality with carat weight to maximize profit, which is why excellent-cut diamonds are rare.
To understand the fascinating process that turns a rough stone into a faceted gem, read our PeonyJewels blog post: Gemstone Cutting: From Rough Stone to Radiant Faceted Gem.
GIA Diamond Cut Grades Proportions Table
| GIA Diamond Cut Grades | Good | Very Good | Excellent | Very Good | Good |
| Table % | 47 – 49 | 50 – 51 | 52 – 62 | 63 – 66 | 67 – 69 |
| Crown Height % | ≤ 8.5 | 9.0 – 10.5 | 11.0 – 16.0 | 16.5 – 18.0 | ≥ 18.5 |
| Girdle Thickness % | 0 – 0.5 | 1.0 – 1.5 | 2.0 – 4.5 | 5.0 – 7.5 | ≥ 8.0 |
| Pavilion Depth % | ≤ 39.5 | 40.0 – 41.0 | 41.5 – 45.0 | 45.5 – 46.5 | ≥ 47 |
| Culet Size % | Pointed – 1.9 | 2.0 – 3.9 | ≥ 4.0 | ||
| Total Depth % | ≤ 55 | 55.0 – 57 | 57.5 – 60 | 60 – 62 | ≥ 65 |
| Star Facet % | < 40 | 40 – 45 | 45 – 65 | 65 – 70 | > 70 |
| Lower Girdle Facet % | < 65 | 70 – 85 | > 90 | ||
| Crown Angle (Degrees) | 26 – 30 | 30 – 31 | 31.5 – 36.5 | 37 – 38 | 38 – 40 |
| Pavilion Angle (Degrees) | 38.2 – 38.8 | 39.8 – 40.4 | 40.4 – 41.8 | 42 – 42.4 | 42.6 – 43 |
IMPORTANT NOTE: Understanding GIA Cut Grading
The GIA Cut Grade is determined by a complex algorithm that takes into account the diamond’s overall brightness, fire, scintillation, weight ratio, and polish/symmetry.
While the proportions and angles listed in this table are the key factors used in the assessment of Round Brilliant Cut diamonds, they represent general acceptable ranges for achieving the listed grade. Crucially, achieving an Excellent or Very Good grade depends on the entire combination of these factors, not solely on whether a single parameter falls within a specific range. This table should be used as a guide to proportions, not as a definitive grading tool.
While an ideal cut creates the most brilliant diamond, cutters often balance cut quality with carat weight to maximize profit. That’s why excellent-cut diamonds are rare.
Other Factors That Affect Diamond Value
5. Fluorescence
When exposed to strong UV light, a diamond may emit a colored glow (most commonly blue). The intensity is graded as NONE, FAINT, MEDIUM, STRONG, or VERY STRONG.
Fluorescence usually doesn’t significantly affect a diamond’s value unless it is Very Strong, which can occasionally make the diamond appear hazy or “milky” in natural light. For fancy colored diamonds, fluorescence can sometimes enhance the color.
For a detailed explanation of this phenomenon and tips on avoiding dull-looking stones, read our PeonyJewels blog post: What Exactly Is a Milky Diamond and Why Should You Avoid It?
6. Diamond Cut Shapes (Fancy Shapes)
Beyond the Round Brilliant
While the Cut grade focuses on a diamond’s light performance (the brilliance and fire), Cut Shape refers to the stone’s geometric outline. Unlike Round diamonds, all other shapes are referred to as “Fancy Shapes.”
Two primary factors influence the shape chosen for diamonds of the same carat weight and quality (Color and Clarity).
- Weight Retention: The rough diamond’s original shape largely dictates the final cut style to minimize weight loss, thus maximizing carat yield.
- Market Demand: Trends and consumer preference heavily influence the demand and pricing of specific fancy shapes. Different cuts can significantly affect the final price compared to a Round diamond of the same grade.
Facet Breakdown by Cut Style
This table provides a generalized breakdown of facet structure across popular cut styles:
| Cut Style | Crown (Upper Part) | Girdle | Pavilion (Lower Part) | Total Facets |
|---|---|---|---|---|
| Brilliant Cut | Full star, bezel, and upper girdle facets (33 facets) | – | Main and lower girdle facets (24 facets) | 57 facets |
| Emerald Cut | Variable, typically 25 facets | Variable, typically 8 facets | Variable, typically 24 facets | 57 facets |
| Marquise Cut | 33 facets | – | 22 facets | 55 facets |
| Oval Cut | 33 facets | – | 22 facets | 55 facets |
| Pear Cut | 33 facets | – | 23 facets | 56 facets |
| Princess Cut | Variable, commonly 40+ facets (Step or Brilliant Style) | Variable | Variable, commonly 16+ facets | 57 facets |
| Trilliant | 7 facets | 3 facets | 9 facets | 19 facets |
| Baguette Cut | 9 facets | 4 facets | 12 facets | 25 facets |
| 16/16 Cut | 1 table, 16 facets | – | 16 facets | 33 facets |
| 8/8 Cut | 1 table, 8 facets | – | 8 facets | 17 facets |
⭐ Expert Buying Tips
- Budgeting: Emerald-cut diamonds (and other Step Cuts) are typically less expensive per carat than Round Brilliant diamonds of the same quality, often allowing you to purchase a larger stone on the same budget.
- Appearance of Size: Princess-cut diamonds often appear about 15% larger than Round diamonds of the same carat weight due to their square shape. Pear shapes can also appear larger.
- Wearing a Pear: Pear-shaped diamonds should be worn with the rounded part at the base of your finger and the pointed end facing outward—a positioning that beautifully elongates the finger.
Common Myths You’ve Heard
7. Are “Hearts & Arrows” a Sign of a Good Diamond?
Hearts & Arrows is not a special cut—it’s a precise pattern that appears in an extremely well-proportioned Round Brilliant Cut. Seeing it doesn’t automatically mean the cut is excellent; it requires proper proportions of the table and pavilion to allow you to see eight arrows on top and eight hearts on the bottom with a viewing tool.
8. Are Diamonds with a “Laser Inscription” Better?
A laser inscription is a GIA code that GIA microscopically etches onto the diamond’s girdle, helping buyers verify the diamond matches its certificate.
- GIA Diamond Dossier: Certificates for diamonds under 1ct (small certificate), which includes the laser inscription by default.
- GIA Diamond Grading Report: Certificates for diamonds 1ct or larger (large certificate), which includes the clarity plot diagram and allows for optional laser inscription.
Quick Fact: A clarity plot diagram shows a diamond’s internal features—like a fingerprint for the stone.
Besides Diamonds, What Other Gemstones Are Good for Engagement Rings?
Colored gemstones have beautiful meanings and have seen a surge in popularity since Princess Kate’s wedding featuring Diana’s 18ct sapphire ring.
- Sapphire: Known as “Imperial Stones,” they symbolize loyalty, wisdom, and eternal love. Their deep blue color and royal appeal make them a popular choice.
- Ruby: Red symbolizes passion, love, and loyalty. A ruby ring is a classic choice to celebrate romance.
- Emerald: Emeralds represent love and life, vitality of spring, success, and guaranteed love.
Ready to Find or Create Your Diamond Piece?
Now that you’ve read this ultimate guide to the 4Cs of diamonds, are you ready for your engagement ring?
At Peony Jewels, we specialize in bringing your unique vision to life. If you dream of a piece tailored just for you, we offer bespoke jewelry customization services. Please contact us directly to begin designing your unique token of love.
Alternatively, for those seeking daily elegance or a special gift, we invite you to explore the exquisite craftsmanship behind our unique handmade vintage earrings collection on our website. Find the perfect piece to elevate your everyday style.
