Round Brilliant Engagement Rings
The round brilliant is the most sparkling diamond shape there is, and it is the only one GIA awards an actual cut grade. That single fact is why it is both the safest shape to buy and the most expensive per carat: you can verify how well it was cut, and cutting it wastes more of the rough than any other shape.
The round brilliant in brief
- Cut style
- Brilliant cut. GIA describes brilliant cuts as characterised by numerous small kite-shaped and triangular facets — a busier pattern with smaller facets, which helps mask inclusions and colour and makes them more forgiving of imperfection than step cuts.
- Facets
- 57 or 58 facets — 58 with a culet facet, 57 with a pointed culet. Eight bezels, eight stars and sixteen upper halves on the crown; sixteen lower halves, eight mains and an optional culet below.
- Length to width
- Not applicable. A round brilliant is circular, so there is no length-to-width ratio to choose. What replaces it is the cut grade — and it is the only shape that has one.
- One carat measures
- About 6.5 mm across. A useful sanity check — carat is weight, not size, and two stones of the same weight in different shapes cover quite different amounts of finger.
Choosing a round brilliant diamond
General four Cs advice is written for round brilliants. Where it differs for this shape, it differs like this.
The only shape with a GIA cut grade
Excellent through to Poor, awarded by GIA to round brilliants alone. Every fancy shape on a report carries polish and symmetry only. This is the most under-explained fact in diamond buying and it is the main reason a round is the safest shape to buy at distance.
Forgiving of colour and clarity
GIA notes the round brilliant's large number of facets and brilliance can hide some inclusions and yellow or brown colour, more so than step cuts. It is the baseline every other shape is compared against.
The most expensive per carat
For a straightforward reason: reaching a circle throws away more of the original rough crystal than any other outline. You are paying for what was cut away.
Setting a round brilliant
The most forgiving shape to set — no points, no corners. GIA does note protecting the pointed tip at the bottom of the stone with the setting, or choosing a stone with a culet facet, which helps prevent chipping. Four claws show the most stone; six hold it most securely.
The wedding ring beside it
The easiest of all, and the benchmark for the others. A straight band sits flush against almost any round setting.
All ten shapes compared, with profile, width and whether to solder the pair.
Where the shape comes from
The angles behind the modern round brilliant were first proposed by Henry Morse of Boston in the 1860s and refined by Marcel Tolkowsky in 1919. GIA introduced a scientific system for assessing round brilliant cut quality in 2005.
Round brilliant diamonds, answered
Why are round diamonds more expensive than other shapes?
Because cutting one wastes the most rough. Reaching a circle from an octahedral crystal discards far more of the original stone than reaching an oval, a cushion or a princess cut — so a one carat round costs more than a one carat fancy shape of the same grades. You are paying for the material that ended up as dust.
Are round diamonds out of style?
No, and they are the one shape that never really goes out. Roughly speaking, fashions move around the round brilliant rather than replacing it — ovals, cushions and now elongated cushions rise and fall, while the round stays the default. If you want a ring that will not date, this is it.
Do round diamonds have bow ties?
No. A bow tie is a feature of elongated brilliant cuts — ovals, pears and marquises — where the stone's length blocks light across its middle. A round brilliant is symmetrical in every direction, so there is nothing for the effect to form in. A round can look dark if it is badly cut, but that is a cut problem, not a bow tie.
Which diamond shape sparkles the most?
The round brilliant, and it is not particularly close. Its 57 or 58 facets are arranged specifically to return the maximum amount of light to the eye, and it is the only shape whose cut quality GIA grades — so you can actually verify that a given stone achieves it. Fancy shapes sparkle differently and sometimes very beautifully, but none is engineered for it as precisely.
How many facets does a round brilliant diamond have?
57 or 58 — 58 when there is a culet facet at the bottom point, 57 when the culet comes to a point instead. That breaks down as eight bezels, eight stars and sixteen upper halves on the crown, and sixteen lower halves plus eight mains below. It is one of the few shapes with a genuinely fixed count; most fancy shapes vary between cutters.
Other shapes
- Oval Engagement Rings
- Radiant Cut Engagement Rings
- Marquise Engagement Rings
- Emerald Cut Engagement Rings
- Cushion Cut Engagement Rings
- Pear Shaped Engagement Rings
- Princess Cut Engagement Rings
- Asscher Cut Engagement Rings
- Heart Shaped Engagement Rings
Undecided is a perfectly good place to start — come and see several side by side, which is the only way to settle it. Before that, the natural and laboratory-grown comparison and the ring size guide are the two things worth reading.
Sources
Gemmological claims on this page are from the Gemological Institute of America. Where GIA gives no figure — facet counts for most fancy shapes, several length-to-width ratios — we say so rather than repeat a trade convention as fact.