Last Updated on 13/07/2021 by Ammy Ammika

Diamond Size Chart Millimeter(MM) To Carat: Which Cut Is the Biggest!

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Did you know that a diamond can be measured in weight (Carat Weight) and size (Millimeters)? Even though the price is set in accordance with its carat weight as it is a standard unit of measurement for diamonds, it is also important to consider its size and ratios to ensure that you receive the best diamond possible, worthy of your budget.

The measurement in millimeters is an indicator of the diamond’s true size. Diamonds with the same carat weight can have different cuts and width and so some shapes may appear larger even though they are made from the same carat size (If you are looking for a diamond cut which is larger than the Round Brilliant Cut, you may try looking for Fancy Diamonds: Emerald Cut, Oval Cut, and Pear Shape).

And in this article, you will get to know all about diamonds in different shapes so that you may estimate the true size of diamonds of different carat weights so that you may find the diamond which is most suitable to you. This will be done via the “Diamond Size Chart”

1. Round Brilliant Cut Diamond


The Round Brilliant Cut Diamond is a classic diamond cut, it is also the most popular diamond cut for engagement rings and wedding rings. The cut is symmetrical, the refraction of light gives off a “brilliant” sparkle with its 58 facets, making the round brilliant cut have one of the most fire and sparkle.

Round Diamond Size Chart

MM SizeCarat Weight
3 mm.0.10 ct.
3.8 mm. 0.20 ct.
4 mm.0.25 ct.
4.25 mm.0.28 ct.
4.5 mm.0.36 ct.
4.75 mm.0.40 ct.
5 mm.0.50 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.
7 mm. 1.30 ct.
7.3 mm.1.50 ct.
7.75 mm.1.75 ct.
8 mm.2.00 ct.

2. Princess Cut Diamond

Princess cut diamond ring
The Princess Cut Diamond is placed just below the Round Brilliant Cut in terms of popularity. It is a perfect square, beautiful and sharp, with an ability to sparkle and refract similar to the round diamond because of the “Brilliant Cut” method used. Using a Princess Cut Diamond in your engagement ring or your wedding ring will make your ring stand out regardless of your gender. Chic and cool is the slogan here.

Princess Diamond Size Chart

MM SizeCarat Weight
2.5 mm.0.10 ct.
3 mm. 0.18 ct.
3.25 mm.0.26 ct.
3.5 mm.0.29 ct.
4 mm.0.40 ct.
4.25 mm.0.45 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.
6.75 mm.1.75 ct.
7 mm.2.00 ct.

3. Cushion Cut Diamond

Cushion cut diamond ring
The Cushion Cut Diamond is one of the five most popular diamond shapes. The Cushion Cut has a “Mixed Cut” technique, a mixture of the Brilliant Cut and the Step Cut, which gives off its unique charm. The shape gives a luxurious feeling, a beautiful mix of classic and modern. Currently, the Cushion Cut is especially receiving more interest as it was used to make Meghan Markle’s ring, a member of the English royal family and celebrity, in which Prince Harry designed himself and has deliberately chosen this diamond cut for it.

Cushion Diamond Size Chart

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.

4. Oval Cut Diamond

Oval cut diamond ring
The Oval Cut Diamond or the Egg-Shaped Diamond is considered a popular choice for engagement rings and wedding rings, suitable for those who like to stand out. The oval shape of the diamond helps elongate the wearer’s fingers as well as appearing larger than other diamonds of the same carat weight. More than that, its sparkle is just as brilliant as the round cut diamonds.

Oval Diamond Size Chart

MM SizeCarat Weight
5x3 mm.0.21 ct.
5x4 mm.0.35 ct.
6x4 mm.0.50 ct.
6x5 mm.0.60 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.
8.5x6.5 mm.1.50 ct.
9x7 mm.2.00 ct.
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.

5. Emerald Cut Diamond

Emerald cut diamond
The Emerald Cut Diamond or the Rectangle Shape Diamond has its cutting technique adapted from gem “Emerald” which is how this cut received its name. This diamond cut is considered popular for vintage-style jewelry. It is unique yet subtle, suitable for both men’s and women’s jewelry. The most charming aspect of this diamond cut comes from its wide diamond table which allows it to receive and reflect light in a different manner from other diamond cuts.

Emerald Diamond Size Chart

MM SizeCarat Weight
3x2 mm.0.10 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.
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.

6. Heart Shaped Diamond

Heart shaped diamond ring
The Heart Shaped Diamond is a symbol of love and romance. Because of its unique heart shape, it is widely used for engagement rings, pendants, diamond earrings, and other accessories. To achieve this diamond shape’s look, the cutting process is extremely delicate as it requires a perfect 1:1 ratio and a Modified Brilliant Cut technique that gives this diamond shape the same brilliance as the round shaped diamonds.

Heart Diamond Size Chart

MM SizeCarat Weight
3.5 mm.0.18 ct.
4 mm.0.25 ct.
4.25 mm. 0.28 ct.
4.5 mm.0.35 ct.
5 mm.0.50 ct.
5.5 mm.0.60 ct.
6 mm.0.75 ct.
6.5 mm.1.00 ct.
7 mm.1.25 ct.
7.5 mm.1.50 ct.
8 mm.2.00 ct.
8.5 mm.2.50 ct.
9 mm. 3.00 ct.

7. Pear Shaped Diamond

Pear shaped diamond ring
The Pear Shaped Diamond is another diamond shape that is a unique classic. Its characteristics include a water drop shape with one end being an arc that harmoniously tapers down into a sharp point. This diamond shape can be used for both engagement rings and wedding rings for that chic factor that no other shapes can offer. This diamond shape can also be worn as earrings and necklaces. Regardless of what form the Pear Shaped Diamond comes in, it will still charm all eyes on them.

Pear Diamond Size Chart

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.
7.7x5.7 mm.1.00 ct.
8x6 mm.1.25 ct.
8.5x6.5 mm.1.50 ct.
8.7x6.7 mm.1.80 ct.
9x7 mm.2.00 ct.

8. Marquise Cut Diamond


The Marquise Cut Diamond is a highly popular choice for stylish jewelry. The diamond is shaped like an eye or a grain of rice, it is suitable for those with larger fingers because it will help elongate your fingers to look more slender and elegant. The shape also appears larger than other diamond shapes of the same carats.

Marquise Diamond Size Chart

MM SizeCarat Weight
5x3 mm.0.20 ct.
6x3 mm.0.25 ct.
7x3 mm. 0.30 ct.
8x4 mm.0.50 ct.
8.75x4.25 mm.0.70 ct.
9x4.5 mm.0.75 ct.
10x5 mm.1.00 ct.
11x5.5 mm.1.25 ct.
12x6 mm.1.50 ct.
13x6.5 mm.2.00 ct.
14x7 mm. 2.50 ct.
15x7 mm.3.00 ct.
16.5x8.25 mm.4.00 ct.

9. Asscher Cut Diamond

asscher diamond ring
The Asscher Cut Diamond has a “Step Cut” technique, just like the Emerald Cut Diamond, but instead of taking its shape from emeralds – its shape is inspired by windmills. In today’s times, this diamond shape is considered quite rare. The reason why this shape is not more popular is that its table width is smaller than other diamond shapes. However, the Asscher Cut is filled with charm and subtle chique; its allure is so prominent that it was used on Princess Madeleine of Sweden’s engagement ring which is filled with a sense of classic beauty and a hint of Art Deco.

Asscher Diamond Size Chart

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.
8 mm.3.00 ct.
8.5 mm.3.50 ct.
9 mm.4.12 ct.
9.5 ct.5.09 ct.

10. Radiant Cut Diamond

radiant diamond ring
The Radiant Cut Diamond is a love child of the Emerald Cut Diamond, Round Brilliant Cut, and the Asscher Diamond Cut. Its shape is completely unique to its own and is one of the most modern diamond cuts. With its considerable size and radiant sparkles, it is rapidly rising in popularity.

Radiant Diamond Size Chart

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.
10x8 mm.3.50 ct.

Perfect Shape, Perfect Size

Lastly, when you are purchasing a diamond, keep in mind that the carat weight may not always indicate the diamond’s size as it will differ from shape to shape with the main reason being the depth of the diamond, especially when viewed from above.
If you have any questions or inquiries about the size of diamonds, you can always contact us for further information.

Photos Credit: CHRIS JACKSON / GETTY IMAGES / Frank Darling

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