Round Brilliant – The Guide to the Most Classic Diamond Cut
The round brilliant is the most iconic and sought-after cut shape – for both natural and lab-grown diamonds. The shape is timeless, universally appreciated and renowned for its unparalleled brilliance.
What is a round brilliant cut?
The cut shape is round from above, with 57 or 58 facets. It is the only shape that can receive the highest official cut classification – “Ideal” according to IGI (for lab-grown) and “Excellent” according to GIA (for natural). Thanks to its perfect symmetry and optimized faceting pattern, it maximizes light reflection – what gives the stone its characteristic sparkle.
History and precision
The shape was mathematically defined by Marcel Tolkowsky in 1919, and has been the standard for brilliance ever since. Today, 3D technology is used to maximize both optics and extraction. Note, however, that up to 60% of the raw material is ground away to achieve perfect round brilliance.
Advantages of round brilliants
Recommended proportions for round brilliants
| Class | Table % | Depth % | Crown angle | Pavilion angle | Ratio |
|---|---|---|---|---|---|
| Ideal / Excellent | 52–62 | 57.5–63 | 31.5°–36.5° | 40.6°–41.8° | 1.00–1.01 |
| Very Good | 50–52 / 62–66 | 56–57.5 / 63–64.5 | 26.5°–31.5° / 36.5°–38.5° | 39.8°–40.6° / 41.8°–42.4° | 1.00–1.01 |
| Acceptable | 47–50 / 66–69 | 53–56 / 64.5–67.5 | 22°–26.5° / 38.5°–40° | 38.8°–39.8° / 42.4°–43° | 1.00–1.02 |
For maximum light play, it is recommended to stay within the Ideal/Excellent range. Read more about proportions and ratio .
Size guide in mm for round brilliant-cut diamonds
| Carat | Diameter (approx. in mm) | See stones |
|---|---|---|
| 0.30 ct | about 4.2 mm | Show |
| 0.50 ct | about 5.0 mm | Show |
| 1.00 ct | approx. 6.4–6.6 mm | Show |
| 1.50 ct | approx. 7.4–7.5 mm | Show |
| 2.00 ct | approx. 8.0–8.2 mm | Show |
| 3.00 ct | approx. 9.2–9.4 mm | Show |
| 5.00 ct | approx. 11.0–11.2 mm | Show |
(Exact measurements may vary depending on the depth of the grind.)
What should you consider when choosing a round brilliant?
Color: Round brilliants hide color very effectively. For white metal, colors D–H are recommended. In yellow gold , I–J work well.
Clarity: The brilliance masks inclusions well. You can choose SI1–VS1 – especially up to 1.00 ct. For larger stones, VS1 or higher is often recommended for optimal visual clarity.
Grinding: Always choose Ideal or Excellent in polish and symmetry. Read more about why grinding is most important .
Common settings for round brilliant diamonds
- Solitaire – maximizes brilliance and play of light.
- Halo – gives the illusion of a larger stone.
- Side stones – classic and balanced expression.
- The Tresten – symbolism and tradition in one.
Lab-grown vs. natural – what about round brilliants?
Both natural and lab-grown round brilliants are cut according to the same principles. The difference lies in origin and price – not in brilliance. All our stones are certified by recognized institutes.
Filter by your preferences
In our selection at Diamant Banken – for both natural diamonds and lab-grown diamonds – you can easily filter by round brilliant, carat, color, clarity and certificate. View round cut stones here .