How to Choose an Oval Diamond: Ratio, Bow-Tie and Outline

An oval diamond has no cut grade on most reports, so the buyer judges it. Length to width ratio, the bow-tie shadow and outline symmetry decide the stone.

An oval diamond looks larger than a round of the same weight, flatters the finger by lengthening it, and sits lower in a setting because it has no sharp corners to protect. Those advantages explain why it has become the most requested fancy shape. The difficulty is that most laboratory reports do not assign a cut grade to ovals, so the judgement that a cut grade would normally make falls to the buyer.

Three things decide whether an oval is a good one.

Ratio

The length to width ratio is the length divided by the width. It sets the whole character of the stone.

Around 1.30 to 1.35 is a softer, fuller oval, closer to a round. It reads as a classic shape and suits shorter fingers, which a long stone can overwhelm.

Around 1.35 to 1.45 is the range most people find balanced. Elongated enough to do the job an oval is meant to do, without looking stretched.

Above 1.50 becomes distinctly long and lean. Striking on a long finger, but the ends become narrow and the stone can look thin from across a room.

There is no correct answer. There is only the answer that suits the hand, and the way to find it is to try two or three ratios side by side.

The bow-tie

Every oval, pear and marquise has a darker band across its middle, running from side to side, shaped like a bow-tie. It is caused by the way the pavilion facets in the widest part of the stone reflect the viewer's own head and shoulders back at them rather than returning light from around the stone.

It cannot be removed. It can be made faint or made severe by the cutter's choices about pavilion depth and facet angles.

A faint bow-tie flickers into view as the stone moves and disappears again. This is normal and, to many eyes, adds depth.

A strong bow-tie is a fixed dark stripe that sits there whatever the angle. It makes the stone look smaller and dead in the middle.

No report measures it. The only way to assess a bow-tie is to see the stone, or at minimum a video of it, moving under ordinary light. A still photograph under a spotlight will hide it.

Outline

Ovals are cut by hand and no two outlines are identical. Small variations are expected. Large ones matter.

Shoulders. The curves between the ends and the widest point should be even and gently rounded. Some ovals have high, boxy shoulders that make the stone look like a rounded rectangle. Others are so narrow at the shoulders that the stone looks like an egg.

Symmetry. Fold the stone in your mind along its long axis and then its short axis. Both halves should match. A slight lopsidedness that is invisible loose can become obvious once the stone is set and a straight band runs under it.

The ends. They should be the same width and the same curve. Pointed or flattened ends are a sign the cutter was chasing weight.

Other things worth checking

Depth. Ovals hide weight easily. A depth percentage much above the mid sixties usually means a stone that looks smaller than it weighs.

Colour. The narrow ends of an oval concentrate colour. Going one grade whiter than you would for a round is a common and sensible adjustment.

Clarity. The brilliant faceting hides inclusions well, but the large table in the centre of a bow-tie region can expose a dark crystal. Check the plot.

Setting. Four prongs on an oval usually sit at the shoulders, which can make the stone look boxy. Prongs placed at the ends protect the tips and keep the outline clean. Six prongs on a large oval is a sensible choice.

An oval is a stone that rewards being seen in person. The report tells you weight, colour and clarity. The ratio, the bow-tie and the outline are judged by the eye, and those are the three that decide whether it is beautiful.

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C'Garden is an independent bespoke jeweller in Kuala Lumpur. We are not affiliated with, endorsed by, sponsored by or certified by any organisation, laboratory or brand named in this article. Third-party names are used only to refer factually to those organisations and their published standards. All text and imagery in this article is original work created by C'Garden.

Reference

Gemological Institute of America. (n.d.). Diamond cut. GIA. https://www.gia.edu/diamond-cut