The oval is one of the most requested shapes for a reason. It carries the brilliance of a round cut in an elongated outline that flatters the hand and reads larger per carat. This guide walks through what genuinely matters when you choose an oval cut lab-grown diamond, and the few things worth avoiding.
Why the oval cut is worth considering
The modern oval is a brilliant cut, which means it is faceted to maximise the return of light to the eye. Its elongated form gives it two practical advantages over a round diamond of the same weight. It presents a larger face-up surface, and it lengthens the finger when worn. For many buyers, that combination is the entire appeal.
Because the shape is so popular, the market offers a wide spread of quality. Two ovals of identical carat weight and certification can look quite different in the hand. Understanding a handful of measurements lets you tell them apart with confidence rather than relying on a single number on a report.
Length-to-width ratio: the shape decision that matters most
The length-to-width ratio describes the outline of the stone. It is calculated by dividing the length of the diamond by its width, and you will find both measurements on the certificate. A ratio of 1.40 means the diamond is 1.4 times as long as it is wide.
There is no single correct figure, because the ideal depends on the look you want. As a working guide:
- 1.30 to 1.50 is the range most buyers find balanced. Within this band the oval looks clearly elongated without appearing narrow.
- 1.35 to 1.45 is the classic sweet spot. It is the proportion most people picture when they imagine an oval, and it sits comfortably in most settings.
- Below 1.30 the outline begins to look rounder and shorter, which some buyers prefer but which reduces the slimming effect on the finger.
- Above 1.50 the stone reads long and slender. This can be a deliberate and elegant choice, though it narrows your setting options and can emphasise any unevenness in the outline.
Ratio is largely a matter of taste, so it helps to view a few examples before deciding. The figure on the report tells you the proportion, but only seeing the shape tells you whether it is the one for you.
The bowtie effect: what to look for and what to avoid
Every oval has a bowtie. It is a darker shadow across the centre of the stone, shaped like a bow, caused by the way light travels through the elongated facets. A faint bowtie is normal and unavoidable in this shape. The question is one of degree.
A well-cut oval shows a soft, barely noticeable bowtie that all but disappears as the stone moves. A poorly cut oval shows a heavy, dark band that stays visible and interrupts the brilliance across the middle of the diamond. This is the single most common flaw to avoid in an oval, and it is not described by any grade on the certificate. You have to look.
When assessing the bowtie, view the diamond face-up under ordinary lighting and tilt it gently. A good stone keeps its light return across the centre. If a dark zone dominates the middle and refuses to brighten, move on. Because the bowtie is invisible on paper, it is one of the strongest reasons to buy from a source that examines each stone before it reaches you.
Proportions: depth and table
Beyond the outline, two proportion figures help separate a lively oval from a flat one. Both appear on the diamond report.
Table
The table is the large flat facet on the top of the diamond, expressed as a percentage of the stone's width. For ovals, a table in roughly the 53 to 63 per cent range tends to balance brightness and fire well. A very large table can make the stone look glassy, while a very small one can mute its sparkle.
Depth
Depth is the height of the diamond from top to bottom, again as a percentage of its width. A depth of about 58 to 64 per cent is a sensible target for ovals. Too shallow and light escapes through the bottom, leaving a glassy or watery centre. Too deep and the stone hides weight underneath, so it looks smaller face-up than its carat suggests.
These ranges are guides, not strict rules. The reliable test remains the eye: a diamond with figures slightly outside the typical band can still perform beautifully, and one with textbook numbers can still show a heavy bowtie. Treat the proportions as a shortlist tool, then judge the stone itself.
Why ovals look larger per carat
Buyers often notice that an oval appears bigger than a round diamond of the same weight, and this is genuinely the case rather than an illusion of marketing. Two factors are at work.
- Surface area. The elongated outline spreads the same weight across a larger face-up area, so more of the diamond is visible from above.
- Shape perception. The eye reads length as size. An elongated stone draws the gaze along its axis, which adds to the impression of scale on the finger.
The practical takeaway is that an oval can offer visible presence at a more considered carat weight than a round equivalent. It is one of the more efficient shapes if face-up size is a priority for you.
Clarity tips for oval diamonds
Oval cut diamonds hide inclusions reasonably well, because their brilliant faceting scatters light and breaks up the view through the stone. That said, the open table of an oval offers less to disguise an inclusion sitting under the centre.
At CRTD we hold a minimum of VS1 clarity across every diamond, so the question becomes where within the higher grades to focus rather than how low you can go. The sensible approach with an oval is to confirm that any inclusion is not positioned directly beneath the table where it would be easiest to see. A clarity grade describes the type and presence of inclusions, but their location matters just as much for an open shape. A stone graded VS1 with inclusions tucked toward the edges will look cleaner to the eye than one of the same grade with a single inclusion under the centre.
Colour tips for oval diamonds
Elongated brilliant cuts can show colour slightly more readily at the ends, or points, of the stone than a round diamond does. If a colourless appearance matters to you, this is worth keeping in mind when comparing grades.
For a setting in white metal such as platinum or white gold, a higher colour grade keeps the stone looking bright and neutral. For yellow or rose gold, a touch of warmth in the diamond is masked by the metal, so a slightly lower colour grade often looks identical face-up and lets you direct your selection elsewhere. As with clarity, viewing the actual stone against the intended metal is more telling than the grade alone.
A short checklist before you decide
- Choose a length-to-width ratio you have actually seen, ideally within 1.30 to 1.50.
- Inspect the bowtie face-up and in motion. Avoid any stone with a heavy, fixed dark centre.
- Use table and depth figures as a shortlist, then judge brilliance with your eye.
- Confirm inclusion placement, not just the clarity grade.
- Match colour grade to your chosen metal.
- Insist on independent certification, IGI or GIA, for every stone.
Frequently asked questions
What is the best length-to-width ratio for an oval diamond?
There is no single best ratio, as it comes down to taste. Most buyers settle between 1.30 and 1.50, with 1.35 to 1.45 being the classic balanced range. Below 1.30 the stone looks rounder and shorter; above 1.50 it looks long and slender. Viewing a few examples is the surest way to find your preference.
Is the bowtie a fault in an oval diamond?
A faint bowtie is normal in every oval and is not a defect. A heavy, dark bowtie that stays visible as the stone moves is the flaw to avoid, because it interrupts brilliance across the centre. The bowtie does not appear on the certificate, so each stone should be examined in person or by someone who inspects it on your behalf.
Do oval lab-grown diamonds look bigger than round ones?
Yes. For the same carat weight, an oval presents a larger face-up surface and its elongated outline reads as greater size on the finger. This makes the oval an efficient choice when visible presence matters to you.
Are oval lab-grown diamonds certified the same way as mined diamonds?
They are. A lab-grown diamond is chemically, physically, and optically identical to a mined diamond, and it is graded by the same independent laboratories, such as IGI and GIA, against the same criteria for cut, colour, clarity, and carat.
Explore oval cut diamonds with CRTD
Every oval we offer is sourced to order, independently certified, and inspected before dispatch, so the stone you receive performs as well in the hand as it reads on paper. Browse our oval cut collection, read the detailed oval cut diamond guide, or learn how we source each stone. You can also view the full range of diamonds to compare shapes side by side.