💎 What Is a Round Cut Diamond?
The round cut diamond, often referred to as the round brilliant cut, is the most popular diamond shape in the world. Known for its timeless appeal and unmatched brilliance, this cut features 58 facets designed to reflect maximum light. It's the classic choice for engagement rings and a favorite for diamond studs, pendants, and other fine jewelry.
Key Features of Round Cut Diamonds:
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Facets: 58
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Shape: Perfectly circular from top view
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Cut Style: Brilliant (maximizes sparkle)
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Popularity: Over 60% of all diamonds sold
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Ideal Length-to-Width Ratio: 1.00 (perfect circle)
📊 Unified Carat ⇄ Millimeter Size Chart (Round Brilliant Cut)
| Carat Weight | Diameter (mm) | MM to Carat Estimate | Notes |
|---|---|---|---|
| 0.25 ct | 4.1 mm | 4.1 mm ≈ 0.25 ct | Petite, great for earrings or delicate rings |
| 0.33 ct | 4.4 mm | 4.4 mm ≈ 0.33 ct | Slightly larger, still dainty |
| 0.50 ct | 5.1 mm | 5.1 mm ≈ 0.50 ct | Balanced sparkle, popular starter size |
| 0.75 ct | 5.8 mm | 5.8 mm ≈ 0.75 ct | Noticeable size without being too bold |
| 1.00 ct | 6.5 mm | 6.5 mm ≈ 1.00 ct | Iconic size for solitaire rings |
| 1.25 ct | 6.9 mm | 6.9 mm ≈ 1.25 ct | Slightly larger face-up presence |
| 1.50 ct | 7.4 mm | 7.4 mm ≈ 1.50 ct | Statement size, high brilliance |
| 2.00 ct | 8.2 mm | 8.2 mm ≈ 2.00 ct | Excellent for center stones |
| 2.50 ct | 8.8 mm | 8.8 mm ≈ 2.50 ct | Luxurious and noticeable |
| 3.00 ct | 9.4 mm | 9.4 mm ≈ 3.00 ct | Bold and brilliant |
| 3.50 ct | 9.9 mm | 9.9 mm ≈ 3.50 ct | Rare and dazzling |
| 4.00 ct | 10.2 mm | 10.2 mm ≈ 4.00 ct | Red carpet-worthy |
| 4.50 ct | 10.7 mm | 10.7 mm ≈ 4.50 ct | Luxuriously large |
| 5.00 ct | 11.0 mm | 11.0 mm ≈ 5.00 ct | Bold statement piece |
| 6.00 ct | 11.8 mm | 11.8 mm ≈ 6.00 ct | Ultra-luxury, rare |
| 7.00 ct | 12.4 mm | 12.4 mm ≈ 7.00 ct | Very high-end, investment quality |
| 8.00 ct | 13.1 mm | 13.1 mm ≈ 8.00 ct | Museum-grade size |
| 9.00 ct | 13.7 mm | 13.7 mm ≈ 9.00 ct | Rare and extravagant |
| 10.00 ct | 14.0 mm | 14.0 mm ≈ 10.00 ct | Heirloom-level, incredibly valuable |
💍 Why Choose a Round Cut?
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Maximum Sparkle: The 58-facet design ensures optimal brilliance and fire.
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Classic Style: Timeless and versatile for all types of settings.
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Excellent Light Performance: Ideal for showcasing clarity and color.
📝 Final Thoughts
Round cut diamonds are a brilliant choice - literally and figuratively. Whether you’re shopping for a ring, pendant, or pair of earrings, this size guide gives you a reliable way to understand how different carat weights translate to visible size. Use this reference to shop smarter and choose confidently.
💎 Note: This size chart is also suitable for moissanite stones, as moissanite and diamonds of the same carat typically share similar millimeter dimensions.
