mm to Carat Stone Size Charts
Metric Sizes to Carat Weights

Choosing the right diamond takes time. Every shape features its own unique characteristics and aesthetics.

Millimeter to Diamond Carat Weight Conversion Chart



Go more in depth with individual shapes by clicking the images on the chart below.

Round Shape Cushoin Shape Radiant Shape Pear Shape Asscher Shape
Oval Shape Princess Shape Emerald Shape Marquise Shape Heart Shape  




Round Diamond Average Carat by Millimeter Conversions

Classic and brilliant, round cut stones are a popular choice for engagement rings in both traditional and modern settings. | Shop Kobelli Round Centered Jewelry.
Approx. Millimeter
Approx. Carat Weight
4
0.25
5
0.5
6.5
1
7
1.25
7.5
1.5
8
2
9
2.5
9.5
3
9.7
3.5
10
4
10.5
4.5
11
5


Oval Diamond Average Carat by Millimeter Conversions

Perhaps the second most popular diamond cut next to round, oval shapes are brilliant, slimming and arguably the most fashion forward choice for engagement rings. | Shop Kobelli Oval Bridal & Fine Fashion Jewelry.
Approx. Millimeter
Approx. Carat Weight
6.5 x 4.5
0.5
8 x 6
1
9 x 7
1.75
10 x 7
2
11 x 7.5
2.5
11.5 x 8
3
12.5 x 8.5
3.5
13 x 9
4
13.5 x 7
4.5
14 x 9.5
5


Cushion Diamond Average Carat by Millimeter Conversions

One of the most unique stones on the market, as well as a Kobelli customer favorite, particularly on our halo rings, cushion cut stones are between a round brilliant, old mine and radiant, with rounded corners for a comfortable look and feel.

Cushion stones vary from elongated to squarish. Kobelli hand selects each of our cushion stones to best fit our designs for the most flattering outcome. | Shop Kobelli Cushion Wedding Jewelry.
Approx. Millimeter
Approx. Carat Weight
4.5
0.5
5.7
1
6.2
1.25
6.5
1.5
7.3
2
8
2.5
8.3
3
8.7
3.5
9
4
9.5
4.5
10
5


Princess Diamond Average Carat by Millimeter Conversions

A traditional stone cut with remarkable brilliance and sparkle, princess cut diamonds are the square alternative of the round brilliant. | Shop Kobelli Princess Luxury Jewelry.
Approx. Millimeter
Approx. Carat Weight
4.4
0.5
5.5
1
5.9
1.25
6.3
1.5
7
2
7.5
2.5
8
3
8.3
3.5
8.7
4
9
4.5
9.3
5


Square Radiant Diamond Average Carat by Millimeter Conversions

As the name implies, radiant cuts give off magnificent radiance and sparkle with its intricate faceting and stunning flair.

A popular choice for our custom orders, Kobelli customers are absolutely in love with this dazzling stone cut. | Shop the Kobelli Radiants.
Approx. Millimeter
Approx. Carat Weight
4.3
0.5
5.5
1
6
1.25
6.5
1.5
7
2
7.5
2.5
8
3
8.5
3.5
8.8
4
9
4.5
9.5
5


Rectangular Radiant Diamond Average Carat by Millimeter Conversions

Rectangular radiant cut diamonds showcase exceptional brilliance through their distinctive facet pattern, delivering captivating sparkle and light performance. This versatile shape combines the elegance of emerald cuts with the fire of brilliant cuts, creating a stone that commands attention from every angle. Perfect for those seeking a diamond that balances sophistication with dazzling visual impact.

A popular choice for our custom orders, Kobelli customers are absolutely in love with this dazzling stone cut. | Shop the Kobelli Radiants.
Approx. Millimeter
Approx. Carat Weight
6 x 4
0.70
7 x 5
1.20
8 x 6
1.70 to 1.90
9 x 6
1.80 to 2.00
9 x 7
2.70 to 2.75
10 x 7
3.00 to 3.25
10.25 x 7.20
3.00
10 x 8
3.90
12 x 8
4.50
11 x 9
5.30


Emerald Diamond Average Carat by Millimeter Conversions

Beloved for its Art Deco appeal, clean cuts and sharp appearance, emerald cut stones give off a breath of fresh air with its gleaming sparkle, unique from that of the more traditional cuts and just as stunning. | Shop Kobelli Emerald Shape Creations.
Approx. Millimeter
Approx. Carat Weight
5.5 x 4
0.5
7 x 4.5
1
7.5 x 5
1.25
8 x 5.5
1.5
8.5 x 6
2
9 x 6.5
2.5
9.7 x 7
3
10 x 7
3.5
10.7 x 7.5
4
11 x 6
4.5
11.5 x 8
5


Pear Diamond Average Carat by Millimeter Conversions

Pear cut diamonds have long been loved for their royal ties and long, slender shape. A challenging stone to cut and set, pear cut jewelry requires absolute skill and perseverance to create. Our pear shape diamonds all come in brilliant-faceted cuts for the brightest sparkle. | Shop Kobelli Pear Diamond Jewelry.
Approx. Millimeter
Approx. Carat Weight
7 x 4.5
0.5
9 x 5.5
1
9.5 x 6
1.25
10 x 6.5
1.5
11 x 7
2
12 x 7.5
2.5
13 x 8
3
13.5 x 8.5
3.5
14.5 x 9
4
15 x 7
4.5
15.5 x 9.5
5


Marquise Diamond Average Carat by Millimeter Conversions

Elegant and rare, marquise cuts hold an air of grandiose extravagance. The slender shape elongates the hand and beautifully carries itself with a romantic flair. | Shop the Kobelli Marquise Collection.
Approx. Millimeter
Approx. Carat Weight
8 x 4
0.5
10.5 x 5.5
1
11.5 x 7
1.25
11.7 x 6
1.5
13 x 6.5
2
14 x 7
2.5
15 x 7.5
3
16 x 8
3.5
16.5 x 8.3
4
17.5 x 6.5
4.5
17.7 x 9
5


Asscher Diamond Average Carat by Millimeter Conversions

Asscher cuts are among the most rare shapes on the market and make for a truly unique piece.

The hall of mirrors effect can be seen by looking into this mesmerizing stone, reminiscent of a lifetime of memories. | Shop the Kobelli Asscher Collection.
Approx. Millimeter
Approx. Carat Weight
4.4
0.5
5.5
1
6
1.25
6.3
1.5
7
2
7.5
2.5
8
3
8.3
3.5
8.6
4
9
4.5
9.7
5


Heart Diamond Average Carat by Millimeter Conversions

The perfect piece for your sweetheart. Show your love with a classic heart shape. | Shop Kobelli's Heart Shaped Diamonds.
Approx. Millimeter
Approx. Carat Weight
5.5 x 5
0.5
7 x 6
1
7.6 x 6.5
1.25
8 x 7
1.5
9 x 8
2
9.5 x 8.5
2.5
10 x 9
3
10.5 x 9.5
3.5
11 x 10
4
11.5 x 7.5
4.5
12 x 10.5
5

FAQ

How much does a listed carat weight vary by?

All diamond weights may vary by 5% unless stated otherwise. One-of-a-kind products will showcase the exact weight of all stones.

Do moissanites weigh the same as diamonds?

Not quite - while the moissanite gemstone is technically slightly lighter in weight due to a lower density, the stones are most commonly marketed by their Diamond Equivalent Weight (DEW) in accordance to the millimeter size of the stone rather than the weight of the stone itself.

All of Kobelli's moissanite products will be listed with the Diamond Equivalent Weights (DEW). This allows for an identical dimensional look if you are to upgrade your existing moissanite center stone for a diamond.

What about other gemstones?

Gemstones, aside from moissanites, will be listed in accordance to either their millimeter size or their carat weight. Every stone type carries its own unique traits for density and depth.