A radiant cut diamond is a square or rectangular stone with its four corners trimmed off, faceted like a round brilliant so it sparkles hard rather than showing the calm, mirror-like steps of an emerald cut. A typical radiant has 70 facets. The caveat is depth: radiants are cut deep, so a 1 ct radiant can look smaller face-up than a 1 ct oval.

What does a radiant cut diamond look like?

A radiant cut diamond looks like a rectangle or square with its corners clipped at an angle, giving it eight short and long sides in outline. Inside that outline, typically 70 small triangular and kite-shaped facets break light into lively flashes, the same effect a round brilliant gives. That mix of a straight-edged outline with brilliant sparkle is why the trade calls the radiant a mixed cut. The style first appeared in the late 1970s.

Which cuts is a radiant most often confused with?

A radiant is most often confused with the cushion cut and the emerald cut, and each comparison turns on one detail. A cushion has softly rounded corners and curved sides, while a radiant has straight sides and sharp clipped corners. An emerald cut shares the radiant’s rectangular outline but has usually 57 long, flat step facets instead, so it shows broad flashes rather than glitter.

We have full side-by-side guides on whether radiant or cushion cut is better and the difference between radiant and emerald cuts.

How big does a 1 carat radiant cut look on the hand?

A 1 carat radiant cut measures roughly 7.00 x 4.98 mm across the top on our own listings, with a depth of about 3.35 mm. That covers about the same finger area as a 6.5 mm round brilliant of the same weight. A 2.00 ct radiant on the same listing measures 8.50 x 6.10 mm. Because the stone is deep, it sits a little higher in the setting than an oval of equal weight.

The 5 Stone Radiant Cut Engagement Ring takes a centre stone of 1.00 to 3.00 ct and is listed from £917 at the time of writing. The Curved Radiant Cut Bridal Set pairs a 1.00 to 2.00 ct radiant with a matching curved band, also from £917 at the time of writing.

What length-to-width ratio should a radiant cut have?

A radiant cut’s length-to-width ratio, its length divided by its width, decides whether it reads as a square or a rectangle. A ratio of about 1.00 to 1.05 looks square. Most buyers choose a rectangle of roughly 1.20 to 1.35, which lengthens the finger. Above about 1.40 the stone looks long and narrow. No ratio is correct; it is a matter of taste.

The ratio you choose changes the look on the hand more than any other single number on the certificate.

Radiant cut ratios and how they look

Ratio (length ÷ width)	Outline	On the hand
1.00 to 1.05	Square	Compact and bright
1.20 to 1.35	Classic rectangle	Lengthens the finger
1.40 and above	Long rectangle	Slim, close to an emerald outline

What should a radiant cut certificate show?

A radiant cut certificate usually names the shape in long form, such as cut-cornered rectangular modified brilliant, and lists the measurements, polish and symmetry. Radiants usually do not receive the overall cut grade that round stones get, so the ratio and depth do that job. IGI, which certifies every CarbonstoneUK centre stone, still grades lab-grown colour and clarity on the familiar scales.

GIA, by contrast, stopped using those colour and clarity scales for lab-grown diamonds on 1 October 2025. To compare radiant cuts against other shapes, see our complete guide to diamond shapes or browse radiant cut rings in stock.

Frequently asked questions

Is a radiant cut the same as a princess cut?

No. A princess cut is a square stone with four sharp, pointed corners, while a radiant has its corners clipped off. Those clipped corners make the radiant less likely to catch and chip at the tips. We do not stock princess cuts, but we stock 2 radiant designs and can make others bespoke.

Does a radiant cut hide inclusions well?

Yes. The many small brilliant facets of a radiant break up the view into the stone, so small inclusions, the tiny natural marks inside a diamond, are harder to see than in an emerald cut. A VS2 clarity radiant usually looks clean to the naked eye at normal viewing distance.

Is a radiant cut cheaper than a round diamond?

Yes, usually. Round brilliants cost the most per carat in both lab-grown and natural diamonds, because cutting a round wastes more of the rough crystal. A radiant of the same weight and grades is typically priced lower. At the time of writing, our lab-grown 1.00 ct radiant rings start from £917.

How many facets does a radiant cut diamond have?

A radiant cut diamond typically has 70 facets, although the exact count varies a little between cutters. Facets are the small flat polished faces that reflect light. For comparison, a standard round brilliant has 57 or 58, and an emerald cut usually has 57 long step facets.

Can a radiant cut be set east-west on the finger?

Yes. An east-west radiant is turned sideways so its long edge runs across the finger rather than along it. The look is modern and less expected. Ask for a ratio of 1.25 or more, otherwise the turn is hard to notice because a near-square stone looks the same both ways.

Are lab-grown radiant cut diamonds real diamonds?

Yes. A lab-grown radiant is the same carbon crystal as a mined diamond, with the same hardness of 10 on the Mohs scale and the same sparkle. Only its origin differs. Each of our centre stones comes with a free IGI certificate stating that it is laboratory-grown.

More guides on this topic

For every other diamond shape, see the main types of diamond cuts.