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Lab Diamond Size Guide

In this article, we’ll go through everything you need to know about lab diamond sizes.

What is a Lab Diamond Size Chart?

A lab diamond size chart is something that helps you understand the millimeter size of each diamond compared to its carat weight. Carat weight alone usually isn’t enough to make a decision on what diamond is best, knowing the millimeter measurements helps you figure out what the best option is depending on your budget.

Each diamond shape will look different depending on its carat weight. Even when lab diamonds are different sizes, their carat weight can still remain the same.

Why is a Diamond's Millimeter Measurement Important?

Knowing a lab diamond’s millimeter measurement is important because it lets you know the true size of it. There are other instances when it can help too, such as when you’re buying a diamond for a ring setting that already exists. It normally needs the exact millimeter size of the lab diamond to make sure it will fit.

A diamond’s millimeter measurement is also important when it comes to diamond shapes that aren’t round, such as emerald and cushion lab diamonds. When you purchase high-quality lab diamonds, you will always be able to know both the millimeter measurements and carat weight of it.

What are “Pointers”?

Pointers is a term regularly used in trade and wholesale. It refers to the diamond millimeter size and carat weight. When the lab diamonds weight under one carat, they can be referred to as pointers. For example, a one-pointer is a 0.01 carat diamond. A two-pointer is a 0.2 carat diamond, and twenty-five pointer diamond refers to a 0.25 carot diamond.

Most Popular Diamond Shapes

There are 9 popular diamond shapes, in the section below we’ll go through how each of them look, their level of popularity, along with what impact size has on the overall visual appearance of each diamond.

Type of Lab Diamond Shapes


Round lab diamonds are the most classic and popular diamond shape. They are most often used for engagement rings. Round diamonds have the most brilliance and maximum sparkle. From the top view, round diamonds appear larger than princess diamonds, emerald, cushion, asscher and radiant diamonds. At the same time, they appear smaller from the top than oval, pear, and marquise diamonds.

MM SizeCarat Weight
0.8 mm. 0.0025 ct.
1 mm. 0.005 ct.
1.15 mm. 0.0067 ct.
1.12 mm. 0.0075 ct.
1.25 mm. 0.01 ct.
1.3 mm. 0.01 ct.
1.5 mm. 0.015 ct.
1.75 mm. 0.02 ct.
1.8 mm. 0.025 ct.
2 mm. 0.03 ct.
2.25 mm. 0.04 ct.
2.5 mm. 0.06 ct.
2.75 mm. 0.08 ct.
3 mm. 0.11 ct.
3.25 mm. 0.14 ct.
3.5 mm. 0.17 ct.
3.75 mm. 0.21 ct.
4 mm. 0.25 ct.
4.25 mm. 0.28 ct.
4.5 mm. 0.36 ct.
4.75 mm. 0.44 ct.
5.0 mm. 0.50 ct.
5.25 mm. 0.56 ct.
5.5 mm. 0.66 ct.
5.75 mm. 0.75 ct.
6 mm. 0.84 ct.
6.25 mm. 0.93 ct.
6.5 mm. 1.00 ct.
6.8 mm. 1.25 ct.
MM SizeCarat Weight
7 mm. 1.30 ct.
7.3 mm. 1.50 ct.
7.5 mm. 1.67 ct.
7.75 mm. 1.75 ct.
8 mm. 2.00 ct.
8.25 mm. 2.11 ct.
8.5 mm. 2.43 ct.
8.7 mm. 2.50 ct.
9 mm. 2.75 ct.
9.1 mm. 3.00 ct.
9.5 mm. 3.35 ct.
9.75 mm. 3.61 ct.
10 mm. 3.87 ct.
10.25 mm. 4.16 ct.
10.5 mm. 4.41 ct.
10.75 mm. 4.57 ct.
11 mm. 4.91 ct.
11.25 mm. 5.49 ct.
11.5 mm. 5.85 ct.
12 mm. 6.84 ct.
12.25 mm. 7.26 ct.
12.5 mm. 7.36 ct.
12.75 mm. 7.52 ct.
13 mm. 8.51 ct.
13.5 mm. 9.53 ct.
14 mm. 10.49 ct.
15 mm. 12.89 ct.
16 mm. 16.06 ct.
17 mm. 18.00 ct.
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Emerald cut lab diamonds are rectangular in shape with trimmed corners. They provide a sophisticated look with elegance. Their design was developed in the 1500s. Since emerald cut diamonds have flat parallel facets, they produce an effect referred to as “hall of mirrors”. These diamonds aren’t as brilliant as round diamonds, they offer a more clean look with clarity and lustre. They are right in the middle when it comes to diamond size, similar to radiant diamonds. Due to their rectangular size, they sometimes give the illusion of appearing larger than they actually are.

MM SizeCarat Weight
3x2 mm. 0.10 ct.
3.5x2 mm. 0.12 ct.
4x2 mm. 0.15 ct.
4x3 mm. 0.20 ct.
5x3 mm. 0.29 ct.
5.5x3.5 mm. 0.46 ct.
6x4 mm. 0.50 ct.
6.5x4.5 mm. 0.75 ct.
6.5x4.5 mm. 0.88 ct.
7x5 mm. 1.00 ct.
7.3x5.3 mm. 1.25 ct.
7.5x5.5 mm. 1.50 ct.
8x6 mm. 1.75 ct.
8.5x6.5 mm. 2.00 ct.
MM SizeCarat Weight
9x7 mm. 2.50 ct.
10x7.5 mm. 3.00 ct.
9.5x7.5 mm. 3.21 ct.
10x8 mm. 3.79 ct.
11x9 mm. 5.21 ct.
12x8 mm. 5.34 ct.
12x10 mm. 6.00 ct.
14x8 mm. 6.25 ct.
13x9 mm. 6.38 ct.
14x10 mm. 8.48 ct.
13x11 mm. 9.13 ct.
14x12 mm. 11.26 ct.
16x12 mm. 14.22 ct.
17x13 mm. 16.50 ct.
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Cushion cut lab diamonds are either square or rectangular in shape. They have rounded corners, sometimes resembling the shape of pillow. This is why they are sometimes called pillow cuts, along with candlelight cuts. They are fiery, but not as brilliant as round diamonds. They have a romantic appeal to them. Cushion diamonds usually look smaller than other diamond shapes, even of similar weight.

MM SizeCarat Weight
4.2 mm. 0.40 ct.
4.9 mm. 0.50 ct.
5.25 mm. 0.75 ct.
5.5 mm. 1.00 ct.
6 mm. 1.25 ct.
6.5 mm. 1.50 ct.
7 mm. 2.00 ct.
7.5 mm. 2.50 ct.
8 mm. 3.00 ct.
8.5 mm. 3.50 ct.
9 mm. 4.12 ct.
9.5 mm. 5.09 ct.
10 mm. 5.62 ct.
11 mm. 7.44 ct.
12 mm. 9.52 ct.
13 mm. 12.66 ct.
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A princess cut lab diamond has great brilliance along with sparkle. They are a classic, with a contemporary look. They are the second most popular choice for engagement rings, after the round diamond. They are the most popular of all the fancy shapes though. The princess cut is very modern, it was created in the 1960s. It has a square outline, with a 1:1 ratio of length-to-width. Sometimes they are slightly rectangular depending on the ratio.

MM SizeCarat Weight
1.5 mm. 0.015 ct.
1.75 mm. 0.03 ct.
2.00 mm. 0.06 ct.
2.25 mm. 0.08 ct.
2.50 mm. 0.10 ct.
2.75 mm. 0.13 ct.
3.00 mm. 0.18 ct.
3.25 mm. 0.26 ct.
3.50 mm. 0.29 ct.
3.75 mm. 0.31 ct.
4.00 mm. 0.39 ct.
4.25 mm. 0.44 ct.
4.50 mm. 0.50 ct.
4.75 mm. 0.64 ct.
5.00 mm. 0.75 ct.
5.25 mm. 0.75 ct.
5.50 mm. 1.00 ct.
5.75 mm. 1.11 ct.
6.00 mm. 1.25 ct.
6.25 mm. 1.39 ct.
6.5 mm. 1.50 ct.
6.75 mm. 1.75 ct.
7 mm. 2.00 ct.
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An oval lab diamond cut is oval in shape. It’s similar to the cushion cut, and very brilliant and fiery. It’s a great alternative if you want something similar to a round diamond, but a bit different in size. When viewed from the top, oval diamonds usually look larger compared to other diamond cuts.

MM SizeCarat Weight
4.5x3.5 mm. 0.21 ct.
5x3 mm. 0.21 ct.
5.5x3.5 mm. 0.33 ct.
5x4 mm. 0.35 ct.
6x4 mm. 0.50 ct.
6x5 mm. 0.61 ct.
6.5x4.5 mm. 0.65 ct.
7x5 mm. 0.75 ct.
7.7x5.7 mm. 1.00 ct.
8x6 mm. 1.25 ct.
9x6 mm. 1.41 ct.
8.5x6.5 mm. 1.50 ct.
9x7 mm. 2.00 ct.
MM SizeCarat Weight
10x8 mm. 2.50 ct.
10.5x8.5 mm. 2.88 ct.
12x8 mm. 3.00 ct.
11x9 mm. 3.85 ct.
12x10 mm. 5.05 ct.
14x10 mm. 5.81 ct.
13x11 mm. 6.05 ct.
14x12 mm. 8.21 ct.
15x12 mm. 8.76 ct.
16x12 mm. 9.32 ct.
16x14 mm. 11.88 ct.
18x13 mm. 12.86 ct.
20x15 mm. 14.96 ct.
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A marquise lab diamond is elliptical in shape. It’s a brilliant cut, and has narrow points at each end. Marquise diamonds have lots of sparkle. When looking from above, it typically appears bigger than any other diamond shapes of similar carat weight.

MM SizeCarat Weight
3x1.5 mm. 0.025 ct.
3.5x1.75 mm. 0.065 ct.
3.5x2 mm. 0.07 ct.
4x2 mm. 0.10 ct.
3.75x1.75 mm. 0.11 ct.
4.25x2.25 mm. 0.12 ct.
5x2.5 mm. 0.14 ct.
5.5x2.75 mm. 0.16 ct.
5.5x3 mm. 0.18 ct.
5x3 mm. 0.20 ct.
6.5x3 mm. 0.23 ct.
6x3 mm. 0.25 ct.
7x3 mm. 0.30 ct.
7.5x3.5 mm. 0.33 ct.
7x4 mm. 0.34 ct.
8x4 mm. 0.50 ct.
8.75x4.25 mm. 0.70 ct.
9x4.5 mm. 0.75 ct.
MM SizeCarat Weight
9.5x2 mm. 0.85 ct.
10x5 mm. 1.00 ct.
11x5.5 mm. 1.25 ct.
11.5x6 mm. 1.33 ct.
12x6 mm. 1.50 ct.
13x6.5 mm. 2.00 ct.
14x7 mm. 2.50 ct.
15x7 mm. 3.00 ct.
14x8 mm. 3.00 ct.
15x7.5 mm. 3.25 ct.
15x8 mm. 3.44 ct.
16x8 mm. 3.86 ct.
16.5x8.25 mm. 4.00 ct.
17x8.5 mm. 4.88 ct.
17.5x10 mm. 5.50 ct.
20x8 mm. 7.08 ct.
20x10 mm. 7.94 ct.
20x11 mm. 9.50 ct.
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Pear cut lab diamonds are a variation of a round cut. It has a pointed end at the top, and is round at the bottom. The pear diamond shape works well for rings, but also pendants and earrings. They are very feminine and brilliant. When viewed from the top, pear cuts usually look larger than most diamond shapes of the same carat weight.

MM SizeCarat Weight
3x2 mm. 0.13 ct.
4x2.5 mm. 0.18 ct.
4x3 mm. 0.21 ct.
5x3 mm. 0.25 ct.
5x4 mm. 0.35 ct.
6x4 mm. 0.50 ct.
6.5x4.5 mm. 0.60 ct.
7x5 mm. 0.75 ct.
7.5x5.5 mm. 0.85 ct.
7.7x5.7 mm. 1.00 ct.
8x6 mm. 1.25 ct.
8.5x6.5 mm. 1.50 ct.
10x6 mm. 1.71 ct.
8.7x6.7 mm. 1.80 ct.
9x7 mm. 2.00 ct.
10x8 mm. 2.50 ct.
11x7.50 mm. 2.61 ct.
13x8 mm. 2.98 ct.
11x8 mm. 3.00 ct.
MM SizeCarat Weight
12x8 mm. 3.00 ct.
12x7 mm. 3.12 ct.
12x9 mm. 3.44 ct.
14x8 mm. 3.47 ct.
13x9 mm. 4.11 ct.
14x9 mm. 4.25 ct.
15x9 mm. 5.06 ct.
14x10 mm. 5.41 ct.
13x11 mm. 5.65 ct.
15x10 mm. 5.75 ct.
16x9 mm. 5.86 ct.
16x10 mm. 6.27 ct.
17x10 mm. 6.46 ct.
15x11 mm. 7.36 ct.
18x11 mm. 8.14 ct.
16x12 mm. 8.99 ct.
18x12 mm. 9.35 ct.
18x13 mm. 10.21 ct.
19x14 mm. 11.70 ct.
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Asscher lab diamond cuts are similar to emerald cuts. They are a square shape with deep corners. Their shape sometimes seems octagonal, appearing sophisticated and large. When viewed from the top, asscher cuts look the same in size to other diamond shapes of similar weight.

MM SizeCarat Weight
4 mm. 0.39 ct.
4.5 mm. 0.50 ct.
5 mm. 0.75 ct.
5.5 mm. 1.00 ct.
6 mm. 1.25 ct.
6.5 mm. 1.50 ct.
7 mm. 2.00 ct.
7.5 mm. 2.50 ct.
MM SizeCarat Weight
8 mm. 3.00 ct.
8.5 mm. 3.50 ct.
9 mm. 4.12 ct.
9.5 mm. 5.09 ct.
10 mm. 5.62 ct.
11 mm. 7.44 ct.
12 mm. 9.52 ct.
13 mm. 12.66 ct.
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Radiant lab diamonds have the sparkle and brilliance of the round diamond, with a similar elegant look of the emerald diamond. It’s perfect for any type of jewelry, especially engagement rings. This diamond cut has trimmed corners, and a slight rectangular shape.

MM SizeCarat Weight
5x3 mm. 0.31 ct.
4.5x3.5 mm. 0.34 ct.
6x3 mm. 0.41 ct.
6x4 mm. 0.50 ct.
6.5x4.5 mm. 0.75 ct.
7x5 mm. 1.00 ct.
7.3x5.5 mm. 1.25 ct.
7.5x5.8 mm. 1.50 ct.
8x6 mm. 2.00 ct.
8.5x6.5 mm. 2.25 ct.
9x7 mm. 2.50 ct.
9.5x7.5 mm. 3.00 ct.
10x7 mm. 3.31 ct.
MM SizeCarat Weight
10x8 mm. 3.50 ct.
11x9 mm. 5.05 ct.
12x9 mm. 6.06 ct.
11.5x10 mm. 6.45 ct.
13x9 mm. 6.54 ct.
12x10 mm. 6.79 ct.
14x10 mm. 8.47 ct.
13x11 mm. 9.33 ct.
13.5x11.5 mm. 10.19 ct.
15x11 mm. 11.48 ct.
14x12 mm. 12.14 ct.
16x12 mm. 14.22 ct.
17x13 mm. 16.22 ct.
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