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· 8 min read

Radiant Cut vs Cushion Cut Diamond: Sparkle, Cost

Radiant cut vs cushion cut diamond, compared honestly: facet patterns, colour retention, length-to-width ratios and what each really costs in CAD.

Both shapes can be square or rectangular and both throw a lot of light, but they are built differently. A radiant has straight sides with clipped corners, so it reads crisp and geometric and it hides warm body colour well. A cushion has rounded corners and a softer outline, and depending on which faceting family it belongs to it either shows large chunky flashes or fine "crushed ice". If you want defined corners and forgiveness on colour, look at radiants first. If you want a softer silhouette and more faceting styles to choose from, start with cushions.

How the two shapes are built

The radiant

GIA describes the radiant as having "70 facets" and calls it "one of the most brilliant of the rectangular shapes", with a "rectangular or square shape and cropped corners" that blends the "sleek, geometric lines of an emerald cut with the dazzling sparkle of a brilliant cut" (GIA, Guide to Diamond Engagement Ring Shapes). GIA also notes that a radiant often shows a "crushed ice" appearance, which "helps mask inclusions and warm colors". That masking effect is the single most useful thing to know about the shape, and it has direct consequences for what you should pay for on the certificate.

The cushion

GIA calls the cushion "a graceful and softly contoured diamond shape" with a "square or rectangular outline combined with rounded corners", often seen as "a cross between a round and a princess cut". Importantly, GIA notes cushions come in two versions, "brilliant and modified brilliant", with the modified version creating the crushed-ice effect.

That last point matters more than most shoppers realise. Two stones both sold as "cushion" can look nothing alike. A cushion brilliant has fewer, larger facets and behaves a bit like an antique cushion, with broad flashes and a more open look. A cushion modified brilliant has extra pavilion facets and fragments the light into small sparkles. You do not have to guess which you are looking at: the shape line on the grading report says so. Read it before you fall for a photograph.

The same trick works for radiants. On a lab report the shape is usually written out as a cut-cornered rectangular or square modified brilliant, not as "radiant", which is a trade name rather than a grading term.

Neither shape gets a cut grade from GIA

This is the honest centre of the comparison. GIA states plainly that "diamond cut grades are only given to round brilliant cut diamonds because they are the only cut that have standardized facets" (GIA, Diamond Cut). In its fancy shape buying guidance GIA repeats that "GIA does not grade the overall proportions of fancy cut diamonds", and points you instead to "Finish, which includes Polish and Symmetry", where Excellent or Very Good indicates solid workmanship (GIA, Expert Tips for Buying Fancy Shaped Diamonds).

Labs do not all agree here. IGI announced on 7 September 2022 that it would begin issuing a cut grade for nine fancy shapes, assessed with a four-step system combining polish and symmetry, proportions guidelines, shape-specific requirements and light return grading. IGI laboratory director Benoit Scheyvaerts described it as using "proportions ranges to identify candidates for the Excellent grade, but our gemologists are now evaluating light return, in addition to polish and symmetry" (National Jeweler, IGI Now Providing Cut Grades for Fancy Shapes, 2022). The shape list includes the square cushion modified brilliant and the cut-cornered square modified brilliant, which is a square radiant. Note what is missing: the elongated rectangular versions of both shapes, which are what most people actually buy, are not on that list. So for a 1.30:1 radiant or a rectangular cushion, you will usually have no overall cut grade from any lab.

With no cut grade to lean on, judge the stone yourself:

  • Polish and symmetry. Very Good or better on both. Good symmetry on a fancy shape is not a disaster, but it is a reason to look harder at the outline.
  • The bow-tie. GIA's fancy shape guidance wants "the 'bow-tie' to be minimized as much as possible". Radiants and elongated cushions both get them. It shows in video, not in a still photo.
  • Millimetre measurements, printed on the report. Compare these, not carat weight, if face-up size matters to you.
  • Depth and table percentages. Deep stones carry weight you never see from above.
  • Video at several angles, tilting. Crushed-ice stones can look lively face-up and grey out at a tilt.
  • Corner alignment on a radiant, and corner symmetry on a cushion. Uneven corners are the most common visible fault in both shapes.

Colour and clarity: where each shape is forgiving

Because a radiant scrambles light, it hides both inclusions and tint, per GIA's own note above. A crushed-ice cushion modified brilliant behaves much the same way. A cushion brilliant, with its larger facets, is the least forgiving of the three: bigger facets mean bigger windows onto whatever is inside the stone.

Practically, that means paying for D or E colour in a crushed-ice radiant is money spent on a certificate rather than on an appearance. G or H set in yellow or rose gold is genuinely fine, and in white metal most people cannot pick G from D once the stone is mounted. Clarity is similar: an SI1 with inclusions scattered under the crown facets of a radiant is often eye-clean, while the same grade in a cushion brilliant can show. Ask for the plot and the video, not just the grade.

If you are shopping lab-grown, one thing changed recently and it affects these shapes specifically. GIA launched its revised laboratory-grown diamond service on 1 October 2025, replacing colour and clarity letter grades with two descriptive categories. "Premium" requires clarity of "Very, Very Slightly included and higher", colour "D", and "Polish, symmetry – Excellent". "Standard" allows clarity down to "Very Slightly included", colour "E-to-J", polish "Very Good", and symmetry "Very Good (or Good for fancy shapes)". The cut grade criterion in both tiers applies to "round brilliant cut diamonds only" (GIA, Updated Laboratory-Grown Diamond Services to Launch October 1). So a lab-grown radiant or cushion with a new GIA document will not carry letter grades at all. If you want the letter grades for comparison shopping, look for an IGI report instead.

Side by side

RadiantCushion
OutlineStraight sides, clipped cornersCurved sides, rounded corners
Report shape nameCut-cornered square or rectangular modified brilliantCushion brilliant, or cushion modified brilliant
Faceting styles availableOne family, generally crushed iceTwo families, chunky or crushed ice
Hides warm colourVery wellWell if modified, less so if brilliant
Hides inclusionsVery wellDepends on faceting family
Bow-tie riskModerate, rises with elongationModerate in rectangular versions
Overall cut grade availableSquare only, IGISquare only, IGI
Setting noteCorners need coverRounded corners sit easily in prongs

Length-to-width is worth a caveat. GIA publishes preferred ratios for ovals, marquises, pears and hearts, but not for radiants or cushions. Any "ideal ratio" chart for these two shapes is a house opinion, including ours: we tend to like squares at 1.00 to 1.05, rectangular radiants around 1.20 to 1.40, and rectangular cushions around 1.10 to 1.25. Your eye is a legitimate tie-breaker here.

What they cost

Both shapes sit below a round brilliant of the same weight and grades, because both waste less rough and because round carries the demand premium. Between radiant and cushion the gap is small. In our own quoting through September 2026, comparable lab-grown radiants and cushions have landed close enough together that faceting style and outline, not shape name, drive the price you see. On the natural side, well-cut rectangular cushions with good symmetry are harder to source than radiants of the same size, and that shows up in the ask.

One thing to check with any Canadian seller: most wholesale diamond lists are quoted in US dollars, so the CAD price you see depends on the rate used. The Bank of Canada published a daily average of 1.4168 Canadian dollars per US dollar on 28 September 2026 (Bank of Canada, Daily Exchange Rates). Ask what rate a quote is built on, and when it was set.

How to choose, in order

  1. Pick the outline first. Look at squares and rectangles on a hand, not on a screen. This decision is aesthetic and nothing else should override it.
  2. Pick the faceting family. For cushions, decide between brilliant and modified brilliant before you compare prices, because they are not competing products.
  3. Set your colour and clarity floor from the faceting, not from a chart. Crushed ice lets you go lower on both.
  4. Filter on polish and symmetry, then watch video. Reject anything with a strong bow-tie or uneven corners, whatever the grades say.
  5. Compare millimetre dimensions across your shortlist before you compare carat weights.
  6. Choose the setting last, once you know the stone's exact measurements, so corner protection and basket depth are right.

What to do next

Browse the loose diamond search and run the same weight in both shapes side by side so you can see how differently they present. When you have two or three candidates, put them into engagement ring settings and preview them in 3D before committing, since a radiant and a cushion of identical weight can look quite different in the same head. Once you have settled on a stone and a setting, finish the ring with metal, size and engraving. If you want more background on grading before you decide, our other guides cover cut grades, colour grades and clarity in more detail.

If you are unsure between a specific radiant and a specific cushion, send us both report numbers. Comparing two real stones is a much shorter conversation than comparing two shapes.

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