Millimeters to Carats

Understanding the relationship between millimeters and carats is essential for both consumers and professionals in the jewelry industry. Carats measure the weight of gemstones, while millimeters measure their dimensions. This conversion is particularly important when assessing the size and value of gemstones, as the weight can significantly influence pricing and desirability.

Typically, the weight of a gemstone in carats can be estimated based on its diameter in millimeters. The following chart provides a general guideline for converting millimeters to carats for round brilliant cut diamonds and similar gemstones:

 

Round Brilliant

Millimeters (mm)	Carat Weight (ct)
7.0 mm	1.00 ct
8.0 mm	2.00 ct
9.0 mm	2.75 ct
10.0 mm	3.50 ct
11.0 mm	4.50 ct
11.5 mm	5.00 ct

 

Oval

Millimeters (mm)	Carat Weight (ct)
8 × 6 mm	1.00 ct
9 × 7 mm	2.00 ct
10 × 8 mm	3.00 ct
11 × 9 mm	4.00 ct
12 × 10 mm	5.00 ct

 

Emerald / Radiant / Asscher

Millimeters (mm)	Carat Weight (ct)
7 × 5 mm	1.00 ct
8 × 6 mm	2.00 ct
9 × 7 mm	3.00 ct
10 × 8 mm	4.00 ct
11 × 9 mm	5.00 ct

 

Cushion

Millimeters (mm)	Carat Weight (ct)
6.5 × 6.5 mm	1.00 ct
7.5 × 7.5 mm	2.00 ct
8.5 × 8.5 mm	3.00 ct
9.5 × 9.5 mm	4.00 ct
10.0 × 10.0 mm	5.00 ct

 

Pear

Millimeters (mm)	Carat Weight (ct)
8 × 5 mm	1.00 ct
9 × 6 mm	2.00 ct
10 × 7 mm	3.00 ct
11 × 8 mm	4.00 ct
12 × 8.5 mm	5.00 ct

 

It is important to note that the actual carat weight can vary based on the specific cut and shape of the gemstone. For example, a round cut diamond may weigh differently than an oval or pear-shaped diamond of the same millimeter measurement. Therefore, while this chart provides a useful reference, it should be used in conjunction with professional evaluation.

In the context of gemstone purchasing, understanding this conversion can aid in making informed decisions. For instance, a consumer seeking a one-carat diamond should be aware that the physical dimensions may vary depending on the cut, which can affect the overall appearance and perceived size of the stone.

Furthermore, the market value of gemstones is influenced not only by carat weight but also by factors such as clarity, color, and cut quality. Therefore, while the millimeters to carats conversion is a useful tool, it is just one aspect of a comprehensive evaluation process.

In conclusion, the millimeters to carats chart serves as a valuable resource for both consumers and professionals in the jewelry industry. By understanding the relationship between these two measurements, individuals can make more informed decisions regarding gemstone purchases and appraisals.