Emerald Cut Diamond Guide: Ratio, Clarity & Size Chart

An emerald cut diamond is a rectangular step cut with cropped corners, made of long parallel facets that create a "hall of mirrors" look instead of the scattered sparkle of a round brilliant. Most emerald cuts have a length-to-width ratio between about 1.30 and 1.50, and because the open facets show inclusions and color more easily, GIA suggests choosing VS2 clarity and G color or better. Below you will find how the cut works, what to look for, a carat-to-millimeter size chart, and the settings that suit it.

What Is an Emerald Cut Diamond?

An emerald cut diamond is a step cut: its facets run in parallel rows, like stairs, around a large flat table. That is different from brilliant cuts such as the round, oval or radiant, whose triangular and kite-shaped facets are designed to break light into many small sparkles.

GIA describes the result as a "hall of mirrors" effect, where broad flashes of light alternate with darker planes as the stone moves. The cut puts the focus on clarity, symmetry and clean lines rather than glitter. The four corners are cut off at an angle, which gives the outline its octagonal edges and removes the sharp points that would be most likely to chip.

Faceting style: step cut (rows of long, rectangular facets).
Outline: rectangle with cropped corners. Very square versions are usually sold as square emerald or Asscher cuts.
Facet count: typically 57 facets, according to Taylor & Hart.
Look: broad flashes and contrast, not "crushed ice" sparkle.

A Short History of the Emerald Cut

The emerald cut was first developed for emerald gemstones, not diamonds. According to GIA, the stepped facets reduced pressure on the brittle emerald crystal during cutting and helped prevent chipping. Cutters later applied the same step-cut technique to diamonds.

The shape became especially popular during the Art Deco period of the 1920s and 1930s, when jewelry design favored geometric outlines and symmetry. That association is why emerald cuts still feel at home in vintage-inspired and Art Deco style rings today.

Ideal Length-to-Width Ratio

Most emerald cut diamonds fall between a 1.30 and 1.50 length-to-width (L:W) ratio, and about 1.40 to 1.50 is widely treated as the classic look. You calculate the ratio by dividing the stone's length in millimeters by its width. A stone measuring 7.0 x 5.0 mm, for example, has a ratio of 1.40.

Published guidance from gem educators and dealers lines up closely:

Source	Recommended L:W range	Notes
Taylor & Hart	1.30 to 1.50	1.40 called "ideal"; 1.40 to 1.50 rated Excellent
International Gem Society	1.30 to 1.60	Most buyers choose around 1.45
Brian Gavin	1.40 to 1.50 (top tier)	1.30 to 1.39 and 1.51 to 1.60 in the next tier
Blue Nile	About 1.40 to 1.50	Described as a preferred range

Lower ratios look squarer and more compact. Higher ratios look longer and slimmer on the finger. The International Gem Society advises avoiding the 1.06 to 1.20 zone, where a stone looks neither clearly square nor clearly rectangular. Within the normal range, the right ratio is a matter of taste.

Because GIA does not issue an overall cut grade for emerald cuts, you judge the cut from the proportions, polish and symmetry on the report. IGI introduced cut grades for nine fancy shapes in 2022, including the emerald and square emerald, so an IGI report may show an overall cut grade for this shape.

Clarity and Color for Step Cuts

Emerald cuts show inclusions and body color more readily than brilliant cuts, so clarity and color deserve more attention. GIA notes that clarity characteristics are typically easier to see in an emerald cut than in a round brilliant, because the long open facets act like a window into the stone.

Clarity

GIA recommends VS2 clarity or higher for emerald cuts, and higher grades again for stones of about 2 to 3 carats and up. The International Gem Society agrees that VS2 is usually eye-clean in step cuts and notes that VS2 inclusions can become visible in stones over roughly 3 carats. Always look at a photo or video of the actual stone, focusing on the area under the table.

Color

The large table also makes body color easier to notice, especially in the corners. GIA suggests G color or better. Warmer metals such as yellow and rose gold can make slightly warmer stones look whiter, which is why the International Gem Society considers lower color grades acceptable in those settings.

For reference, Grown Leo's IGI certified loose emerald cut lab grown diamonds are graded D to F in color and VVS1 to VS2 in clarity with an Excellent cut, which sits inside GIA's suggested range.

Emerald Cut Diamond Size Chart (0.5 to 5 Carats)

An emerald cut diamond of 1 carat measures about 7.0 x 5.0 mm face-up, and a 2 carat measures about 8.6 x 6.3 mm. The table below shows Grown Leo's approximate face-up sizes. Actual measurements vary with each stone's depth and ratio.

Carat weight	Approximate face-up size (length x width)
0.5 ct	5.6 x 4.0 mm
0.75 ct	6.4 x 4.5 mm
1 ct	7.0 x 5.0 mm
1.25 ct	7.5 x 5.4 mm
1.5 ct	8.0 x 5.8 mm
1.75 ct	8.4 x 6.0 mm
2 ct	8.6 x 6.3 mm
2.5 ct	9.2 x 6.8 mm
3 ct	9.8 x 7.2 mm
3.5 ct	10.6 x 7.6 mm
4 ct	10.8 x 7.9 mm
4.5 ct	11.6 x 8.3 mm
5 ct	11.6 x 8.5 mm

To compare these sizes with other shapes and see them on a hand, use the diamond size chart and on-hand simulator. To estimate what a given size might cost, try the lab grown diamond price calculator.

One note for moissanite shoppers: moissanite is less dense than diamond (specific gravity about 3.22 versus 3.52), so a moissanite with the same millimeter size weighs less in carats. Shop moissanite by millimeter size rather than by carat to get the look you expect.

Best Settings for an Emerald Cut

An emerald cut works in almost any setting, but designs that frame its straight lines tend to suit it best. GIA points to minimalist, Art Deco and vintage-inspired designs, and notes that the elongated outline flatters the hand.

Solitaire: keeps attention on the step facets and the clean outline. Four prongs, one at each cropped corner, are the most common choice.
Three-stone: side stones such as tapered baguettes or smaller step cuts echo the center stone's geometry.
Halo or hidden halo: adds sparkle around a center stone that is calm by design.
Bezel: a metal rim around the stone gives a sleek, modern look and covers the edges.
East-west: setting the stone sideways across the finger is a popular modern variation.

When a ring has side stones, match their color to the center stone so the step-cut center does not look darker or warmer by comparison.

Emerald Cut Lab Grown Diamond and Moissanite Options

Both lab grown diamond and moissanite are available in the emerald cut, and the main differences are hardness, optical behavior and price.

Property	Lab grown diamond	Moissanite
Material	Carbon (same as mined diamond)	Silicon carbide
Mohs hardness	10	9.25
Refractive index	2.417	about 2.65 to 2.69
Dispersion (fire)	0.044	0.104
Optical character	Singly refractive	Doubly refractive

Moissanite's dispersion is more than twice that of diamond, so an emerald cut moissanite shows more colorful flashes, while an emerald cut diamond shows a crisper, more neutral hall-of-mirrors look. Which you prefer is personal. Our comparison of moissanite vs diamond covers the trade-offs in depth.

At Grown Leo you can shop emerald cut lab grown diamond rings, emerald cut moissanite engagement rings and loose emerald cut moissanite. Rings are offered in US sizes 4 to 12; check your size with the ring size chart before ordering.

Frequently Asked Questions

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

Most emerald cut diamonds have a length-to-width ratio between 1.30 and 1.50, and many dealers treat about 1.40 to 1.50 as the classic look. The International Gem Society says most buyers choose around 1.45. Lower ratios look squarer, higher ratios look longer and slimmer, so the best choice within that range comes down to personal taste.

What clarity should I choose for an emerald cut diamond?

GIA recommends VS2 clarity or higher for emerald cut diamonds, and higher grades for stones of about 2 to 3 carats and above. The long, open step facets make inclusions easier to see than in a round brilliant. Always review a photo or video of the actual stone and check the area under the table before buying.

Does an emerald cut diamond look bigger than a round?

An emerald cut often looks longer on the finger than a round of the same weight because of its elongated outline. Using Grown Leo's size chart, a 1 carat emerald cut measures about 7.0 x 5.0 mm, while a 1 carat round measures about 6.4 mm across. Whether it reads as bigger depends on the stone's depth and ratio.

Why do emerald cut diamonds sparkle less than round diamonds?

Emerald cuts are step cuts with long, parallel facets, so they produce broad flashes of light and contrast, often called a hall of mirrors effect, instead of the many small sparkles of a brilliant cut. They are not less bright by design; they simply show light in larger, calmer planes. Many buyers choose them for exactly this look.

What is the difference between an emerald cut and an Asscher cut?

Both are step cuts with cropped corners. An emerald cut is rectangular, usually with a length-to-width ratio of about 1.30 to 1.50, while an Asscher cut is square, around 1.00 to 1.05, with larger cropped corners that give it an octagonal look and an X or windmill pattern when viewed from above.

Is an emerald cut moissanite a good alternative to a diamond?

Emerald cut moissanite offers the same step-cut outline at a lower price. Moissanite rates 9.25 on the Mohs scale versus 10 for diamond, and its dispersion is more than twice that of diamond, so it shows more colorful flashes. Buyers who want the crisp, neutral hall-of-mirrors look often prefer diamond; those who like extra fire often prefer moissanite.

Emerald Cut Diamond Guide: Ratios, Clarity, Sizes and Settings