Diamond Size Chart: MM to Carat Conversion

Understanding the true value of diamonds involves more than just its sparkle and allure. When it comes to shopping for these popular stones, knowing their precise weight is crucial. Navigating the world of carats and millimeters can be a bit confusing. But fear not! We’re here to demystify the process for you. In this guide, we’ll walk you through the simple steps to convert millimeters to carats, helping you make informed decisions with confidence.

Diamond Cut & Shape Guide

Why is a Millimeter Measurement Important?

A diamond’s millimeter measurement refers to its diameter, providing an accurate gauge of its size. This differs from carats, which measure weight. Since carat weight can differ due to factors like facets, shape and cut, millimeters offer a more accurate way to measure a stone’s size.

Understanding a diamond’s millimeter size is important, especially when a specific jewelry style or setting demands a particular stone size. This is particularly important when you’re purchasing non-round diamonds, like emerald or cushion cuts, where millimeters reveal the stone’s square or rectangular proportions.

If you’re looking to buy a diamond with a larger appearance (one that looks bigger when viewed from the top), consider fancy shapes like emerald, pear or oval cuts. These shapes tend to appear larger than other cuts.

What are Pointers?

Pointers refer to a specific way of measuring the weight of small diamonds. To understand pointers, you first need to know about carats.

A carat is a unit of measurement for gemstones, equivalent to 200 milligrams. One carat is divided into 100 points for precise measurement down to the hundredth decimal place. For instance, a jeweler might refer to a 0.25-carat stone as ‘twenty-five pointer’ and a 1.08-carat stone as ‘one point oh eight carats.’

Generally, a higher carat weight means a more expensive diamond. But it is important to remember that a diamond’s value isn’t only determined by its carat weight. The 4Cs of diamond, which include the diamond cut, diamond color, diamond clarity, and the diamond carat weight – play an important role in assessing and determining a diamond’s overall value.

Round Diamonds

The round brilliant diamond is the most popular shape, especially for diamond engagement rings. With 57 facets, it offers the best brilliance. This is the MM to carat weight chart you need for brilliant round diamonds.

Round MM Size	Round Carat Weight (Approx.)
4 mm	0.23 ct.
5 mm	0.47 ct.
6 mm	0.8 ct.
7 mm	1.25 ct.
8 mm	2 ct.
9 mm	3.75 ct.
10.1 mm	4 ct.

Oval-Cut Diamonds

The oval cut is quite similar to the traditional round brilliant cut but slightly elongated, which can give it a bigger look. It has 58 facets that maximize the stone’s brilliance. Oval diamond rings and other jewelry exude elegance and can be flattering on the wearer. When picking your stone, use this carat-to-millimeters chart to determine its size.

Oval MM Size	Oval Carat Weight (Approx.)
3×2 mm	0.06 ct.
4x3mm	0.12 ct.
5×3 mm	0.21 ct.
6×4 mm	0.43 ct.
7×5 mm	0.76 ct.
8×6 mm	1.15 ct.
9×7 mm	1.76 ct.
10×8 mm	2.5 ct.
12×10 mm	5 ct.

Emerald-Cut Diamonds

An emerald-cut diamond has a rectangular shape with soft and rounded corners. It has 57 facets that are elongated, straight parallels with a flash of brilliance and sparkle similar to a round or cushion diamond. To know the true size of your emerald-cut diamond, use this mm to carat weight chart.

Emerald MM Size	Emerald Carat Weight (Approx.)
3×2 mm	0.09 ct.
4×3 mm	0.2 ct.
5×3 mm	0.32 ct.
6×4 mm	0.65 ct.
7×5 mm	1.17 ct.
8×6 mm	1.9 ct.
9×7 mm	2.89 ct.
10×7 mm	3 ct.
12×10 mm	6 ct.

Cushion Cut Diamonds

A cushion cut has a rectangular or square shape with rounded edges that resemble a pillow. It has 58 facets that give the stone its captivating brilliance and appearance. This mm to ct conversion will help you tell the true size of a cushion-cut diamond.

Cushion Rectangular MM Size	Cushion Rectangular Carat Weight (Approx.)
4×3 mm	0.2 ct.
5×3 mm	0.34 ct.
6×4 mm	0.53 ct.
7×5 mm	0.97 ct.
8×6 mm	1.6 ct.
9×7 mm	2.5 ct.
10×7.5 mm	3 ct.

Cushion Square MM Size	Cushion Square Carat Weight (Approx.)
4 mm	0.25 ct.
5 mm	0.69 ct.
6 mm	1.2 ct.
7 mm	1.91 ct.
8 mm	3 ct.
8.9 mm	4 ct.
9.4 mm	5 ct.

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Pear Cut Diamonds

The pear-shaped diamond is also called a modified brilliant cut because it is a blend of the oval cut and the Marquise with one pointed end and one rounded end. It has 57 facets, and is quite similar in style and brilliance to a round brilliant stone. This diamond mm to carat will help you figure out the actual size of your pear-shaped stone.

Pear MM Size	Pear Carat Weight (Approx.)
6×4 mm	0.4 ct.
7×5 mm	0.71 ct.
8×5 mm	0.76 ct.
8.5×6.5 mm	1.5 ct.
9×7 mm	2 ct.
10×8 mm	2.5 ct.
12×8 mm	3 ct.
14×9 mm	4 ct.

Princess-Cut Diamonds

A princess-cut diamond is a square-shaped stone popular among engagement rings. It has 57 facets and is often referred to as a modern alternative to a round brilliant. Use this mm to carat chart to find the true size of a princess cut diamond.

Princess MM Size	Princess Carat Weight (Approx.)
5.5 mm	1.05 ct.
6 mm	1.45 ct.
6.5 mm	1.7 ct.
7 mm	2.4 ct.
8 mm	3 ct.
9.4 mm	5 ct.
10.5 mm	6 ct.

Heart Cut Diamonds

The heart-shaped diamond is one of the most sought-after shapes. It features 57 triangular and kite-shaped facets that give the stone its fire and brilliance. Use the chart to determine the size of your heart-shaped diamond.

Heart MM Size	Heart Carat Weight (Approx.)
5 mm	0.5 ct.
6 mm	0.75 ct.
6.5 mm	1 ct.
7.5 mm	1.5 ct.
8 mm	2 ct.
8.5 mm	2.5 ct.
9 mm	3 ct.

Marquise Cut Diamonds

Marquise cut diamonds are known for their pointed ends and elongated elliptical shape. A marquise diamond has 58 facets and a long and narrow shape that creates the illusion of a bigger stone. To know the carat to mm conversion, see the chart below.

Marquise MM Size	Marquise Carat Weight (Approx.)
7×3.5 mm	0.3 ct.
8×4 mm	0.5 ct.
9×4.5 mm	0.75 ct.
10×5 mm	1 ct.
12×6 mm	1.5 ct.
13×6.5 mm	2 ct.
14×7 mm	2.5 ct.
15×7 mm	3 ct.

Radiant Cut Diamonds

Radiant-cut diamonds are typically rectangular but can also be square. They are part of the step-cut family and have 70 facets that enhance the stone’s brilliance. Use the conversion chart below to convert mm to carat for a radiant cut.

Radiant MM Size	Radiant Carat Weight (Approx.)
4×3 mm	0.2 ct.
5×3 mm	0.35 ct.
6×4 mm	0.65 ct.
6.5×4.5 mm	0.75 ct.
7×5 mm	1 ct.
7.5×5.8 mm	1.5 ct.
8×6 mm	2 ct.
9×7 mm	2.5 ct.
9.5×7.5 mm	3 ct.

Asscher-Cut Diamonds

An Asscher cut is a variation of an emerald cut featuring a square step-cut. It has 58 facets and a high crown that enhances the stone’s brilliance. See the mm to carat size chart to determine the actual size of an Asscher diamond.

Asscher MM Size	Asscher Carat Weight (Approx.)
4 mm	0.36 ct.
5.5 mm	1 ct.
6.5 mm	1.5 ct.
7 mm	2 ct.
7.5 mm	2.5 ct.
8 mm	3 ct.

Baguette Cut Diamonds

A baguette-cut stone has elongated parallels with a rectangular and thin shape. It has 14 facets and is often used as a side stone or accent stone for diamond rings. Use this diamond carat to mm chart to check the true size of your baguette stone.

Baguette MM Size	Baguette Carat Weight (Approx.)
1×0.6 mm	0.002 ct.
2×1 mm	0.02 ct.
3×1.5 mm	0.07 ct.
4×2 mm	0.11 ct.
6×3 mm	0.38 ct.

At Angara, we masterfully cut each stone to maximize its brilliance and color. This means no matter what diamond shape you choose, you’ll get one that’s absolutely beautiful rather than one with just a higher carat weight. Explore our diamond collection today.

Frequently Asked Questions:

Q1. How many MM is 1 carat?

The size of a one-carat stone in mm will vary drastically depending on the shape of the stone. For diamonds that are of equal distance from side to side and from top to bottom, like a round or square diamond, a one-carat stone will be equivalent to roughly 4.5-5.5 mm. For elongated fancy-shaped diamonds, a one-carat can be approximately 10×5 mm.

Q2. How many MM is 2 carats?

A 2-carat round or square diamond typically ranges from 7 to 8 mm.

Q3. How many MM is 3 carats?

A 3-carat round or square-shaped diamond will likely be at least 8 mm or closer to 9.25mm.

Q4. What are some typical MM to carat conversions for popular shapes?

Typical MM to carat conversions vary by shape: for round diamonds, 6 mm is around 1 carat, while an oval diamond of the same carat weight might be around 7.7×5.7 mm. For emerald cuts, a 1-carat stone is approximately 7×5 mm.

Q5. How can I use MM to carat conversion charts?

You can use MM to carat conversion charts to estimate the carat weight of a diamond based on its diameter. Simply find the diamond’s measurement in millimeters on the chart and match it to the corresponding carat weight; this will help you assess size and value more accurately.