Diamond Size Chart Millimeter (MM) to Carat

Sharif Khan
Sharif Khan
Last Updated    EST 
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The best way to measure diamonds is in millimeter. Since diamonds are purchased in carat weight (a standard unit of measurement for diamonds), it is helpful to also measure diamonds in millimeters to determine its surface size as well as ratios such as length-to-width ratios in fancy shape stones in order to choose the best diamond for right budget.

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Diamond Size Chart

Are you interested in knowing the size of a diamond in millimeters based-off its carat weight? 

You can use the diamond chart below to help you understand the millimeter (mm) size of round cut diamonds.

The Round Diamond Sizes

Round MM SizeRound Carat Weight
0.8 mm.0.0025 ct.
1 mm.0.005 ct.
1.12 mm.0.0067 ct.
1.15 mm.0.0075 ct.
1.25 mm.0.01 ct.
1.3mm.0.01 ct.
1.5mm.0.015 ct.
1.75mm.0.02 ct.
1.8mm.0.025 ct.
2mm.0.03 ct.
2.225mm.0.04 ct.
2.5mm0.06 ct.
2.75mm.0.08 ct.
3mm.0.11 ct.
3.25mm.0.14 ct.
3.5mm.0.17 ct.
3.75mm.0.21 ct.
4mm.0.25 ct.
4.25mm.0.28 ct.
4.5mm.0.36 ct.
4.75mm.0.44 ct.
5mm.0.50 ct.
5.25mm.0.56 ct.
5.5mm.0.66 ct.
5.75mm.0.75 ct.
6mm.0.84 ct.
6.25mm.0.93 ct.
6.5mm.1.00 ct.
6.8mm.1.25 ct.
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.
8.5mm.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.

Why Diamond Millimeter measurements are important

The measurement of a diamond millimeter will inform you about its actual size. This is because diamond weighing similar carat weight can have different faceting and maybe be larger than the equivalent carat weight. In case you are interested in a diamond that has a larger surface, it is important that you consider getting a diamond that is well cut. Shapes such as pear, emerald and oval are known to have a larger look compared to their round counterparts; overall round cut is still considered to have a large surface size though.

If you are buying a diamond that is already set in an existing setting, measuring the millimeter of the diamond will help you estimate the carat weight of the diamond. However, it may be tricky to get it measured accurately. It is best to seek the advice of a local jeweler in such cases (note: local jewelers are notorious for misleading consumers, so make sure you consult a reliable jeweler).

It is also important to consider millimeter measurements when buying non-round diamond shapes such as emerald and cushion. This is because the measurements of the millimeter will reveal if the diamond rectangular or square, also if it is too shallow or deep (big table or large depth).

There will be more rectangular measurements for emerald cut diamonds, and the square ones are referred to as asscher cuts.

When buying diamonds, the millimeter measurements and carat weight can be found on the grading reports.


One popular term you will always hear from a wholesaler or a trader is pointers. A pointer is equivalent to carat weights. One pointer refers to 0.01 carat diamond. This term is used when we describe melees in the 1-2mm range (small accent diamonds found on jewelry and engagement rings).

With each diamond being unique, it is important that you teach yourself on the average millimeter sizes of various carat weight diamonds to make it possible to find the right option. Read the grading reports of the diamonds for best ways to measure their millimeters.

The Round Diamond Size

This is considered by many as one of the most popular diamond shape. Round brilliant cut diamonds are aesthetically pleasing and versatile. At a reasonable finish and proportional cut, the brilliant cut diamond which is 57-58 faceted rounds is capable of outshining other types of diamond in the market. The round diamonds size does affect the saturation of the stone color, light and clarity performance.

The Princess Diamond Size

Please refer to our princess cut diamonds chart guide for detailed information.

The closest rivals to the round brilliant cut are the princess cut diamonds. This excellent square shape offers sharp and beautiful alternative to the round cut diamonds. The princess cut diamond does cost less than the round cut.

Light performance is one of the most variable features of the princess cut diamond. A princess cut is capable of having an immaculate sparkle in any size. However, as each facet shine becomes more brilliant, the larger the diamond will be.

The Cushion Diamond Size

Please refer to our article on cushion cut diamonds for detailed assessment.

Cushion cut diamond compromises the round cut diamond and shapes with sharp edges and corners. This cushion diamond is known to be of vintage style although it ranks among the top five popular diamond cuts. This diamond is also known to be prominent in jewelry put on by celebrities and royalty.

With cushion cut modernization, culets detracted from the unique cushion diamond beauty have been reduced to ratios unnoticeable and the appearance of the facet has grown more delicate and smaller. The cushion cut diamonds do show more clarity and faceting with their increasing size.

The Emerald Diamond Size

Please refer to our guide on emerald cut diamonds for detailed assessment.

This diamond does resemble gems with rectangular shapes. Just like the cushion cut diamonds, the Emerald diamond corners are also soft and rounded. It is known to be among the most common vintage style jewelry diamond cuts and for pairing with synthetic or real emeralds. Due to the elongated emerald cut diamond, they at times lose some shine.

The Pear Diamond Size

Please refer to our article on pear cut diamonds for detailed assessment.

Pear diamond also referred to as the teardrop shaped can be compared to the oval diamonds on uniqueness scale. However, you can use this cut to create the nontraditional and one of kind engagement rings. The diamonds are usually used in solitaire necklaces and earrings.

Color is known to be an excellent feature of the pear cut diamonds. However, the tip is known to lose some of the color in its smaller sized carats although the body and bottom of the diamond do not.

The Marquise Diamond Size

Please refer our detailed guide for assessing asscher cut diamonds .

In all the finished and correctly cut Asscher diamond is the windmill design. This pattern comes by as a result of step cut that is similar to the emerald diamonds. However, the step cut does not diminish in smaller Asscher diamonds as the patterns do become more compact.

Radiant Diamond Size

Please analyze and examine the details of radiant cut diamonds in our detailed guide.

It is a combination of both the Asscher, round and emerald cut diamonds. It goes by many names and it does make one of the modern stones available in the market. However, characteristics never vary from a single size carat of radiant diamond to another.

Effects of Carat on the Price

Please read our detailed article on diamond price factors.

Since diamonds are priced in relation to per carat basis, carat does have the biggest impact on the price. As the carat increases, so is its price. For instance, the 2 carat is not the 1 carat double price because it is getting harder to get rough materials that are better enough to be cut into one large and single sized diamond.

Here is how the price will be affected by the carat. All these diamonds have the excellent cut, VS2 clarity and H color to make comparison easier. However, the only difference is in the size of the carat.

We do have magic numbers for carat weight in the  diamond industry. There are the 2.0, 1.5, 1.0, 0.75, 0.5 and thereafter every carat half. It is the point at which there is great jump in price. The price doubles at each point. There is clarity, cut and color which also play a role in determining the final price of the diamond.

Reasons Why You Should Prioritize Carat

Definitely, you are aspiring to hit a certain number of carats. However, this should never be your only top priority. You should instead think of focusing on getting the best cut. Having a great cut will make the diamond be livelier and can hide mask color and flaws and can also make the diamond larger.

The left diamond is good cut and is 1.00 carat. It has a 6.2x6.3mm surface area.

The right diamond is of excellent cut and weighs 0.92 carats with a surface area of 6.2x6.2mm.

Despite the two diamonds having different sizes of carat, they all have the same surface area. However, due to the poorer cut of the initial one, up to 10% of the weight of carat is wasted.

Although the left diamond hits 1 carat, it will never sparkle as much compared to the one on the right. For $500 lesser, the diamond with 0.92 carat found on the right is better to purchase. This explains why one should never prioritize weight of carat. Weight will never do much when you cannot even see it and not even a single person will be interested in a lackluster diamond.

Choosing Diamond Size

When you are looking for a diamond to buy, it is important that you always consider the weight of the carat and understand millimeter size do vary for diamonds having similar weight. Since diamonds are precisely cut using machine, there can at times be slight variations which can be caused by inclusions or other types of factors in the diamond.

The millimeter size can also be affected by the depth of the diamond from face up view.

In case you are concerned about the sizing of the diamond, you need to remember that you can always contact a gemologist concerning the best proportions for that particular shape. There are diamonds which are lowly priced than expected since their millimeter size is less than the right size. However, you will have to consider the size of the diamond against factors like color and clarity. It is very productive to make a greater compromise in order to get a larger diamond.

Factors to consider when you Lack larger budget

It is a fact that very few individuals are in a position to afford the 2 carat stone. There are quite a huge number of people who struggle to get to the 1 carat mark. Below are some of the options you can consider when on a budget.

Consider using the settings to make the diamond look bigger

Halo is one of the most common settings that contain small diamonds rings around the diamond center. The setting offers a serious bling that makes it appear as if the diamond located at the center is huge. A thing pave band is another great setting you can go with. You will make the center stone pop when you set the main diamond that is within the small diamonds band. Keep in mind that both the larger diamond center and the thinner band will appear.

In case you are not sure of the type of shape and style to select, you can always visit James Allen inspiration Gallery or the Blue Nile before purchasing an engagement ring The feature will make it possible for you to view the real images of people that have bought rings in the past and help you in deciding the best style for you. The side stone or 3 stone is the worst setting that tries making the diamond appear larger. The hick and heavy bands are never of great help to the smaller diamonds.

Get a diamond that is slightly below the magic numbers

Magic numbers do vary with a range of 0.5 carats. The diamond sellers are capable of fetching more with these weights. In case you go below the magic number, you can always get a diamond for as much as 25% low.

Factor in the Fancy Shaped Diamond

Going for shape besides round is one of the great suggestions. The fancy cut diamonds will not only appear larger, they are also cheaper compared to the round cuts. They are also unique and appealing to females who like standing out in crowds.

Get lower in clarity and color

It is already clear that you should never sacrifice the cut. However, you can get lower in clarity and color in order to reduce the price. Provided the cut is excellent, it does matter if there are other flaws, the diamond will always appear brilliant.

It is recommended that a minimum VS2 clarity and H color although you can get lower to a J color when you don’t mind a warmer appearance. There are amazing SI2 diamonds when you get one which is eye clean.

Final Thoughts

Carat is known to be one of the most difficult things to advise on due to its personal choice. We do understand if there is a goal one wants to hit. We suggest that you do not prioritize it at the expense of the ring's overall beauty.

It is important that one concentrates on getting the best cut that is within their budget. Any well-cut diamond will beautifully sparkle, and it is much better to have a great diamond than just a big one.