Emerald Cut Diamond Ratio: Length-to-Width Guide for Every Look

What is the length-to-width ratio of an emerald cut diamond?

The length-to-width ratio describes the shape of a diamond's outline. You find it by dividing the stone's length by its width. An emerald cut measuring 7.00 × 5.00 mm has a ratio of 1.40, which means it is 40% longer than it is wide. A ratio of 1.00 would be a perfect square, and a ratio of 2.00 would be twice as long as it is wide.

The emerald cut is a step cut. Instead of the small triangular and kite-shaped facets of a brilliant cut, it has long, flat facets arranged in parallel rows, like the steps of a staircase, running around a rectangular outline with cut (bevelled) corners. Most emerald cuts have about 50 to 58 facets, usually three rows of steps on the crown (the top half) and three or four on the pavilion (the bottom half). The cut corners are there for a practical reason: they remove the sharp points that would otherwise chip. For the history, grading and everything else about the shape, see our full emerald cut diamond guide.

On a grading report from GIA or IGI, a fancy shape's measurements are listed as length × width × depth in millimetres, for example 7.02 × 5.01 × 3.40 mm. Many reports do not print the ratio itself, so you work it out: 7.02 ÷ 5.01 = 1.40. The same method applies to every shape, and our explainer on how length-to-width ratios work across every shape shows the typical ranges for ovals, pears, cushions and more. If a term here is new to you, the plain-English jewellery glossary defines it.

One point worth knowing early: GIA does not give emerald cuts an overall cut grade the way it does for round brilliants. The report grades polish and symmetry, but whether the stone is well proportioned is left to you and your jeweller. The ratio is the first, and easiest, part of that judgement. The emerald is one of the step-cut family in our guide to all 34 diamond cuts side by side.

What is the ideal emerald cut diamond ratio?

There is no ideal ratio in the sense of a correct answer. The ratio is mostly a matter of taste, and every range below can be cut beautifully or badly. What the ratio does decide is the character of the stone: compact and architectural at the square end, sleek and elegant at the long end.

Traditional cutters often aimed for about 1.50, and that number still gets quoted as the textbook emerald cut. In practice, most stones on the market today sit somewhere between about 1.35 and 1.50, because that is where the rough crystal is used most efficiently and where most buyers' taste falls. If you are drawn to the longer, slimmer look, our guide to long, slim elongated emerald cuts covers the extra checks they need.

At the other end, once an emerald cut drops below about 1.10 it starts to overlap with the Asscher, a square step cut with larger corners and a higher crown. Our page on where a square emerald meets the Asscher explains how to tell the two apart on a report and by eye.

How does the ratio change the size of an emerald cut on the finger?

For the same carat weight, changing the ratio redistributes the stone's area rather than adding to it. A longer stone gains length and loses width. Because the eye tends to read length as size, a 1 ct emerald cut at 1.60 usually looks a little bigger on the hand than a 1 ct at 1.20, even though the face-up area (the area you see from above) is almost the same.

The next table gives typical sizes across common weights for an emerald cut of about 1.45. Treat them as a starting point: depth changes everything. A stone cut deep carries weight below the girdle (the outer edge) and faces up smaller; a shallow one spreads wider but risks losing brightness.

Emerald cuts are cut deeper than many brilliant shapes, so they tend to face up a touch smaller per carat than an oval or a pear of the same weight. To see how every shape compares on face-up size, read which diamond shapes look largest for their weight. If maximum length for the weight is the goal, emerald cuts above about 1.60 are the natural place to look.

Which emerald cut ratio suits your hand?

Ratio interacts with the finger in predictable ways. These are general patterns, not rules, and trying shapes on is always the real test:

• Shorter or wider fingers: 1.40–1.60 adds length and makes the finger look slimmer.
• Long, slender fingers: almost anything works; 1.20–1.40 adds width and presence without looking stretched.
• Larger stones (2 ct and up): many people prefer 1.30–1.45, because a very long 3 ct can extend past the knuckle.
• East-west settings: where the stone sits sideways across the finger, a ratio of 1.40–1.60 shows the horizontal line most clearly.
• Earrings and pendants: 1.30–1.50 is the usual choice; very long stones can look like bars rather than emerald cuts.

Ratio also affects how the step pattern reads. Emerald cuts do not sparkle in pinpoints like a round brilliant; they show broad flashes of light and dark that move as the stone tilts, known as the flashing hall-of-mirrors pattern. A longer stone shows longer steps and a more pronounced, stretched pattern; a squarer one shows a tighter, more concentric look.

How do depth, table and corners work with the emerald cut ratio?

The ratio sets the outline. Depth, table and corners decide whether that outline is bright or dull. As a rough guide, many well-cut emerald cuts sit at a total depth of about 60–70% and a table (the large flat facet on top) of about 60–70% of the width. These are wide ranges because step cuts are judged more by how they look than by any single number.

The biggest risk is windowing: a washed-out, see-through patch in the centre of the stone where light passes straight through the bottom instead of reflecting back. It happens when the pavilion is too shallow for the stone's size. Elongated stones are slightly more prone to it, because cutters sometimes keep them shallow to maximise length. Our guide to windowing, the washed-out patch in the centre shows what to look for in photos and video.

Corners change the outline too. Large cut corners make a stone look more octagonal and softer; small corners make it look crisper and more rectangular. Two stones with the same 1.45 ratio can look quite different because of corner size alone. Check that all four corners are even: lopsided corners are easy to spot in a step cut, where the parallel lines make any imbalance obvious.

Watch the step pattern as well. You want the steps parallel and evenly spaced, with a clean keel line (the ridge where the pavilion facets meet at the bottom) running down the centre. Good contrast between light and dark steps is what gives emerald cuts their depth; our explainer on why step facets flash in broad planes covers this in more detail.

Colour and clarity matter more in a step cut than in a brilliant. The open, mirror-like facets show inclusions (internal features) clearly, so many people choose VS2 or better. Body colour also tends to gather at the ends of longer stones, so for an emerald cut above about 1.60 in white gold or platinum, G or H colour is a common choice; in yellow or rose gold, I or J can still look white.

How does the emerald cut ratio compare with Asscher, radiant and other shapes?

The radiant cut is the emerald's closest relative: the same rectangular outline with cut corners, but faceted with brilliant-style facets that hide inclusions and give far more sparkle. If you like the emerald's outline but want more fire, compare the two in emerald vs radiant compared on sparkle and price.

If you are drawn to the square end of the range, read our emerald vs Asscher side-by-side before deciding, as a 1.05 emerald and an Asscher look surprisingly different once set. For the wider picture, our overview of all the main diamond shapes places the emerald among the other cuts.

Which setting suits each emerald cut ratio?

The cut corners protect an emerald cut far better than sharp corners would, but the corners are still where the stone is most exposed. Most settings place a claw on each corner. How ratio affects the choice:

• Four-claw solitaire: works at any ratio; on long stones above 1.60, slightly heavier claws help hold the corners securely.
• Double claws (eight claws): two claws per corner, popular on larger stones and on squarer ratios where the corners are broad.
• Bezel or half-bezel: a rim of metal around the edge, very secure and modern; it slightly reduces the visible size, which matters more on small stones.
• Three-stone: straight or tapered baguette side stones or trapezoids either side suit 1.30–1.50, extending the step-cut lines.
• East-west: the stone set sideways; 1.40–1.60 shows the horizontal line most clearly.
• Halo: a frame of small diamonds that follows the outline; it can make the stone read as larger, especially on smaller or squarer emeralds.

For worked examples at different ratios, see setting styles matched to each emerald proportion. If you are still weighing the shape itself, everything else about the emerald cut covers clarity, colour and care.

Does the emerald cut diamond ratio affect price, natural or lab-grown?

Ratio has a much smaller effect on price than carat, colour and clarity. Within the classic 1.30–1.50 range, two stones with the same grades usually cost about the same. Very elongated stones and true square emeralds are less common in larger sizes, so they can take longer to find and sometimes carry a modest premium, but there is no fixed rule.

Emerald cuts usually cost less per carat than a round brilliant of the same grades, partly because the step cut keeps more of the rough crystal. Our page on price per carat across the main diamond shapes sets out the pattern. Because step facets show inclusions, clarity has a stronger effect on what you can comfortably choose than it would in a brilliant cut, and a radiant cut with the same outline can let you go down a clarity grade.

Emerald cuts are cut from both natural and laboratory-grown diamond, and the two look identical to the eye. Lab-grown diamonds are real diamond, grown in a laboratory rather than mined, with the same hardness (10 on the Mohs scale) and refractive index (about 2.42); they cost much less. Natural emerald cuts are rarer. Both should come with an independent grading report that states the measurements, so you can calculate the ratio, and whether the stone is natural or lab-grown.

These are broad ranges only. Prices move with the market and with exact grades, depth and cutting quality.

How do you choose an emerald cut ratio? Step by step

1. Decide the look. Squarer (1.00–1.30), classic (1.30–1.50) or elongated (1.50 and above).
2. Calculate the ratio. Divide length by width from the report's measurements, for example 7.02 ÷ 5.01 = 1.40.
3. Check face-up size. Compare the millimetre length and width, not just the carat weight.
4. Check depth and table. Look for roughly 60–70% for each, then confirm by eye.
5. Watch a 360° video. Look for windowing in the centre, even corners, parallel steps and strong light-dark contrast.
6. Match colour and clarity to the ratio. VS2 or better for most step cuts; G–H colour for long stones in white metal.
7. Plan the setting. Make sure each corner is protected before you commit to the stone.

For ratio ranges across every other shape, use our ratio calculator and shape-by-shape ranges.