There is no single answer to the question of the best cut for a lab-grown diamond ring. But the question itself is usually not quite the one the buyer means to ask. When most people search for the "best cut," they are really asking about shape: round, oval, emerald, pear, cushion. Shape is the first thing the eye notices, and it sets the entire character of a ring.
This guide walks through each shape, what makes it distinct, who it suits, and how it performs in everyday wear. Cut grade matters too, but it is a separate decision, and one that is simpler to resolve.
Here is a clear, complete guide to the best cut for lab-grown diamond rings.
Cut Grade and Shape: Two Different Questions
Cut grade and shape are often confused, but they mean different things. Cut grade measures how precisely a diamond is proportioned and finished, and it is graded Excellent to Poor. Shape describes the outline: round, oval, emerald, cushion, pear, and so on. When someone searches for the "best cut," they are almost always really asking about shape. That is what this guide covers.
Round Brilliant
The round brilliant is the benchmark. Its standard 57 to 58 facet arrangement is engineered specifically to maximise brilliance, brightness and fire. It remains the most popular engagement ring shape worldwide. Classic and versatile, the round brilliant hides minor inclusions well, has no vulnerable points, and wears reliably day to day.
Every other shape in this guide gets measured against it. Because a round brilliant's dense faceting masks inclusions effectively, buyers can often prioritise cut quality and carat weight without needing the highest clarity grades. The round brilliant also receives a formal cut grade from GIA and IGI, making it the only shape with a standardised, standalone cut assessment.
Oval, Cushion and Princess
Oval shares the round brilliant's facet style and brilliance in an elongated silhouette that visually lengthens the finger. Its greater surface area can make it appear larger than a round of the same carat weight. Watch for the bow-tie shadow in a poorly proportioned stone; a well-cut oval will have a minimal or non-existent bow-tie. Cushion softens the corners for a warmer, "crushed ice" sparkle with a romantic, vintage-leaning feel, and its rounded corners wear well daily. Princess keeps the brilliant facet style in a square outline for a modern, geometric look, but its corners are the most vulnerable of the three and need protective prong work.
Pear and Marquise
Both are elongated, brilliant-style shapes that show more visible surface area per carat than a round, so they read larger and lengthen the finger. Pear adds a teardrop point at one end; marquise comes to a point at both ends. Dramatic and distinctive, these are the least forgiving shapes for daily wear, both need a protective V-shaped prong setting at the point. Symmetry is extremely important for both: each half should mirror the other exactly. A well-cut marquise or pear will display a minimal to no bow-tie pattern.
Emerald and Asscher
These step cuts use fewer, larger, flat facets for a calm hall of mirrors flash rather than round's scattered sparkle. This is an art deco, quietly glamorous look. Because the open facets show more of what is inside the stone, a buyer choosing emerald or Asscher may want to prioritise clarity more than they would with a brilliant-cut shape. Emerald cuts do not hide inclusions as well as brilliant cuts due to their long rectangular facets, so higher clarity is important. They are also less scintillating, which means they look best on diamonds with higher colour grades.
Radiant and Heart
Radiant combines a rectangular or square outline with round's brilliant facet style for extra sparkle, and its cropped corners wear more safely than a true point. Introduced in 1977, it boasts the fire of a round brilliant cut in a rectangular or square shape. Heart is the most overtly romantic and symbolic shape. It is best kept above roughly 0.75 carats so the two lobes read clearly, and it needs the most careful prong work of any shape here. A well-shaped heart requires good clarity and symmetry, with well-rounded lobes that match in size and shape.
Choosing Cut Grade Once You've Picked a Shape
Once shape is settled, go as high on cut grade as the lab offers and the budget allows. For a round brilliant, that is Excellent. IGI grades cut on the same Excellent-to-Poor scale for most fancy shapes too. GIA currently limits its traditional overall cut grade to round brilliants only.
One current fact worth flagging: since 1 October 2025, GIA no longer issues that standalone cut grade on lab-grown diamond reports at all. It now uses a Premium or Standard Quality Assessment, a composite designation built from colour, clarity, polish, symmetry and, for round brilliants only, cut. Premium is the top tier, not a cut grade under a new name. IGI made no equivalent change.
Cut Quality Across LOHR's Collection
Every shape LOHR carries, round, oval, emerald, pear and Asscher across the Engagement Rings and Signature Collection, is selected and set with cut quality as the priority. Photos and screens flatten how a cut actually moves light, so the most reliable way to compare shapes side by side is in person at the Brisbane showroom or over a virtual consultation.
The Bottom Line
For maximum sparkle, choose round brilliant. For a flattering, elongating look, choose oval, pear or marquise. For a soft, romantic feel, choose cushion. For a quieter, vintage look that rewards higher clarity, choose emerald or Asscher. Whichever shape wins, go as high on cut grade as the lab offers, and remember that a current GIA lab-grown report shows Premium or Standard, not a cut letter grade.
Browse LOHR's engagement ring and Signature collections by shape, or book a consultation to compare shapes in person or virtually.
