Round Cut Lab-Grown Diamonds: Where They Fit in the U.S. Range
Round cut lab-grown diamonds no longer lead lab-grown demand in the U.S. Oval does, as per The Knot’s 2026 Real Weddings Study. Round still tops all engagement rings, at 26% against oval’s 25%. Here is where the round belongs in a range.
Where Round Cut Lab-Grown Diamonds Stand in U.S. Collections
Lab-Grown Data vs All-Diamond Data
The Knot’s 26% figure covers every engagement ring, lab-grown and natural together. Lab created diamonds were 61% of center diamonds in 2025, so a one-point lead is thin. Natural shoppers still choose round first. Lab-grown shoppers choose oval.
Why Round Remains a Core Shape
Stuller’s Katelyn Meche says the oval has grown there, but round still leads. Marion Fasel said the National Jeweler round is still No. 1, though oval is everywhere. Both are opinions. Neither is sales data. So keep round as the core, with an oval beside it.
What Round Cut Diamonds Offer a Retailer
Facets and the Bow-Tie
A round brilliant has 57 facets, or 58 with a small culet facet, as per GIA’s anatomy page. It shows no bow-tie, the dark band GIA researchers say elongated shapes almost always produce. GIA’s cut grade was built around rounds, so round cut diamonds arrive with a graded cut.
Certification on Round Diamonds
Round lab-grown diamonds can be certified by GIA, IGI, AGS or GCAL, though it is optional. Since October 1, 2025, GIA’s Premium tier needs Excellent cut and Standard needs Very Good, on rounds only. A round below Standard gets no GIA assessment. An IGI lab-grown round report shows a cut grade, the growth process and a treatment line.
Pricing Reality
No public source we found shows a round premium at lab-grown wholesale. Edahn Golan’s Q3 2026 list prices range from $73 to $142 a carat. Rounds are down 9% in a year, 2 carat rounds down 20%, fancy shapes down 9.5%. Golan sees early steadying but no confirmed bottom. The index is still down over 90% since 2018. So treat the round as a core assortment. Do not treat it as an investment.
Princess Cut as a Companion
A loose princess cut diamond adds a square outline next to round. The setting matters more than the price. GIA warns that princess corners chip easily, since they are close to a cleavage plane. It recommends bezels, partial bezels or V-shaped prongs. We found no public wholesale gap between princess and round for lab-grown, so price from your own supplier quotes.
Marquise Cut Diamonds Alongside Round
Interest Without a Number
Marquise cut diamonds are 8% of all engagement center diamonds in The Knot’s 2026 study, against 26% for round. Stuller names marquise among the shapes with the biggest gain in popularity this past year. No public figure gives a growth rate.
What to Verify Before Sourcing
GIA gives no cut grade for fancy shapes, so a marquise report tells you less than a round one. You need to check the shape yourself before you order.
- Set a length-to-width band before you send an inquiry. GIA’s research range is 1.5 to 2.5, and its consumer guide suggests 1.75 to 2.25.
- Ask your supplier for photos or videos of every marquise. Reject any with a dark bow-tie across the middle.
- Inspect both tips. They should line up and show no inclusions.
- Order V-prong settings to protect those tips.
- Read what each report grades. An IGI lab-grown marquise report shows a cut grade. GIA does not.
- Ask for GCAL 8X if cut quality is your selling point. According to Stuller, it covers lab-grown marquise.
- Get a report for every diamond. Reports cover one diamond each, so a parcel quote alone proves nothing.
Final Say
In short, keep round as your core shape, with an oval beside it and marquise as a companion. But a shape says little on its own, so read each diamond’s report first. GDC lists round and marquise among its twelve shapes, and retailers can apply for access to its CRBN platform.
