Diamond Size Chart

Diamonds can be measured in both carat weight and millimeter. While diamonds are purchased based on carat weight — the standard unit of measurement for loose diamonds — it's important to consider millimeter measurements and ratios to choose the best possible option for your budget.

Why is a diamond's millimeter measurement important?

A diamond's millimeter measurement tells you its true size. That's because a diamond of the same carat weight can have slightly different faceting and therefore look larger than a carat weight equivalent. If you're looking for a diamond that looks larger faceup, consider getting a fancy shape diamond: Shapes like emerald, oval and pear often look larger than their round counterparts.

Additionally, if you're purchasing a diamond for an existing ring setting, you'll want to look at the millimeter measurements. Depending on the style of the setting, you may need to select a diamond with a precise millimeter size.

Millimeter measurements are also important to consider when purchasing non-round diamond shapes like cushion and emerald. That's because the millimeter measurements will indicate if the cushion diamond is squarish; emerald diamonds will have more rectangular measurements.

(Just check out our diamond sizing charts below to see the corresponding carat weights for well-cut diamonds.)

When shopping for diamonds, the carat weight and the millimeter measurements can always be found on the GIA certificate of the diamond.

What are "pointers"?

A trade and wholesaler term you may hear is "pointers," which is the equivalent to certain millimeter sizes and carat weights. A "one-pointer" refers to a 0.01 carat diamond, and so forth. These terms are typically used when describing smaller accent diamonds on diamond engagement rings or jewelry. While each diamond is unique, be sure to educate yourself on average millimeter sizes of different diamond carat weights in order to find the best possible option.

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Round Diamond Size Chart

The most popular shape for engagement rings, the round brilliant diamond is versatile and aesthetically pleasing. At an ideal proportional cut and finish, the 57-faceted round brilliant cut diamond can literally outshine most other diamonds on the market. The size of a round diamond affects the stone’s color saturation, clarity and light performance.

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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Princess Diamond Size Chart

Princess-cut diamonds are the biggest competition to the round brilliant cut. The perfectly square shape provides a beautiful, sharp alternative to round-cut diamonds, and a princess-cut diamond will cost also considerably less than a round cut. (That's because more of the rough diamond is used, not wasted, and the price reflects the jeweler’s savings.)

The princess cut diamond’s most variable characteristic based on size is light performance. In any size, a princess cut can have an immaculate sparkle (due in part to the retention of the original rough diamond), but the shine of each facet becomes more brilliant the larger the diamond is.

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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Cushion Diamond Size Chart

The cushion-cut diamond is a compromise between the round-cut diamond and shapes with sharp corners and edges (princess, rectangle, etc.). The cushion cut is a vintage style, but today it ranks among the five most popular diamond cuts. Cushion cuts are especially prominent in jewelry worn by royalty and celebrities.

With the modernization of the cushion cut, the culets that detracted from the original cushion-cut diamond’s beauty have reduced to unnoticeable ratios, and the facet appearance has grown smaller and more delicate. With increasing size, cushion-cut diamonds show more faceting and clarity.

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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Emerald Diamond Size Chart

Emerald-cut diamonds resemble rectangle-shaped gems, but like the cushion cut, their corners are softer and more rounded. They're one of the more popular diamond cuts for vintage-style jewelry and for pairing with real or synthetic emeralds. Because of the elongated shape of emerald-cut diamonds, they sometimes lose a bit of shine, but even a 0.25-carat emerald-cut diamond can easily appear almost twice as big.

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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Oval Diamond Size Chart

The oval cut is a popular choice for women who prefer unique, non-mainstream jewelry. Like emerald-cut diamonds, oval-cut diamonds have an elongated shape and slimming effect on the hand. When an oval-cut diamond is cut to ideal depth proportions, it has a similar brilliance to round-cut diamonds. They brighten as carat size increases.

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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Pear Diamond Size Chart

Pear-cut (or teardrop-shaped) diamonds are comparable to oval-cut diamonds on the uniqueness scale. Although this cut can be used to create one-of-a-kind, nontraditional engagement rings, these diamonds are more commonly used in earrings or solitaire necklaces.

Color is a prominent characteristic of pear-cut diamonds, especially in the rounded bottom part of the stone. The tip loses some of its color in smaller-sized carats, but the bottom and body of the diamond do not.

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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Marquise Diamond Size Chart

The marquise (a.k.a. football-shaped) cut is a popular stone shape in vintage and antique jewelry. It's another diamond style that looks larger compared to other cuts and shapes. The number of facets in a marquise-cut diamond can change dramatically, depending on size — anywhere from 50 to 60 facets is not uncommon.

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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Asscher Diamond Size Chart

In the center of all properly cut and finished Asscher-cut diamonds sits a windmill design. This pattern forms as a result of a step cut, similar to that of emerald-cut diamonds. The step cut style doesn't diminish in smaller-carat Asscher diamonds; the patterns simply become more compact.

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 Diamond Size Chart

This cut is a combination of the emerald, round and Asscher cut diamonds. The unique but elegant style goes by many names (usually "emerald" or "rectangle modified" cut), and it makes for one of the most modern stones on the market. Characteristics don't vary from one carat size of radiant-cut diamond to another; the entire stone just becomes a more compact version of a larger one, adding to its uniqueness.

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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Selecting a Diamond Size

When shopping for a diamond, consider the carat weight, and understand that millimeter size can vary for diamonds of the same carat weight. While diamonds are cut precisely using machinery, slight variations can be caused by inclusions or other natural factors in the diamond. A diamond's depth can also affect the millimeter size from a face-up view.

If you're concerned about diamond sizing, remember that you can ask a gemologist about the ideal proportions for that shape. Some diamonds are priced lower than expected because their millimeter size is less than ideal. Be sure to consider diamond size against other factors like clarity and color — it's counterproductive to make a significant compromise just to get a larger diamond.

Gemologist Buying Tips

Critical or Magic Weights: Buying a diamond below certain carat weight cutoffs will provide larger savings. Consider a diamond at 1.40ct vs. 1.50ct, for example. The visual difference is very small, but the savings can be large.

Choose diamonds that are cut very well. Those diamonds tend to have less depth and more spread. This means their measurements are larger, making the diamond look visually larger than its carat weight. Cut is a crucial element to consider — it can make all the difference.

Carat tends to be the most visual and popular of the 4 C's. You should consider the carat weight first. But remember: Carat weight isn't the only thing that matters. It should be balanced with other factors like cut, color and clarity.

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