How to Measure a Moissanite Diamond?

Moissanite is measured in length rather than carats. The weight of natural diamonds is measured in carats. Moissanite is measured in millimeters rather than carats because it is about 10% lighter than a natural diamond.

However, contrasting the two is simple. A 6.5 mm round moissanite diamond, for example, would be equivalent to a 1 carat diamond of the same size, but would weigh less. They would appear the same to the others.

 All gems have a carat weight, however are sold in various ways. Measuring Moissanite diamonds are offered by their calibrated size, not by their weight.

On the other hand, rubies are marketed by their carat weight. Appears straightforward enough, right?

The Chart Comparing The Sizes of Moissanite and Diamonds

The metric weight of a gemstone will vary depending on the gem's cut and style, even if the gem's diameter remains the same.

Use the following size and form chart as a guide when shopping.

Look for the shape you want

Second, locate the desired carat weight by scrolling down and looking exclusively within that shape. The moissanite carat weight is listed next to it.

Example: A 9.5mm round moissanite weighs 3 carats.


Moissanite Round mm size to carat size comparison

6.5mm is about 1.00CT

7.5mm is about 1.50-1.75ct

8.5mm is about 2.0ct

9mm is about 2.50-2.70ct

9.5mm is about 3.0ct

10mm is about 3.5-3.6ct

10.5mm is about 4.20ct

11.0mm is about 4.75ct

11.5mm is about 5.37ct

12.0mm is about 6.13ct


Moissanite Oval mm size to carat size comparison

7x5mm is about 1.00ct

8x6mm is about 1.50-1.70ct

9x7mm is about 2.0ct

9.5x7mm is about 2.20ct

10x7mm is about 2.82ct

10x7.5mm is about 2.87ct

10x8mm is about 3.0ct

11x9mm is about 4.20ct

12x10mm is about 5.80ct

14x10mm is about 7.75ct


Moissanite Pear mm size to carat size comparison

8x5mm is about 0.90-1.00ct

9x6mm is about 1.50-1.70ct

10x7mm is about 1.90-2.01ct

12x8mm is about 3.50-3.60ct

13x9mm is about 4.70ct


Moissanite Emerald mm size to carat size comparison

7x5mm is about 1.05ct

8x6mm is about 1.50-1.75ct

9x7mm is about 2.5-2.6ct

10x8mm is about 3.20-3.50ct

11x9mm is about 4.90ct


Moissanite Radiant mm size to carat size comparison

 6x4mm is about 0.70ct

 7x5mm is about 1.20ct

 8x6mm is about 1.80ct

9x7mm is about 2.95ct

10x8mm is about 3.90ct

11x9mm is about 5.30ct


Moissanite Cushion mm size to carat size comparison

6.0mm is about 0.90-1.00CT

7.0mm is about 1.50-1.70ct

7.5mm is about 2.0ct

8mm is about 2.4-2.50 ct

8.5mm is about 2.5-2.8 ct

9mm is about 3.0-3.3ct

9.5mm is about 4.0-2.4ct

10mm is about 5.50-5.80ct

10.5mm is about 5.80ct


Moissanite Elongated Cushion mm size to carat size comparison

8x6mm is about 1.61ct

9x7mm is about 2.47ct

9.5x8mm is about 2.69ct

10x8mm is about 3.58ct

11x9mm is about 5.0ct

12x10mm is about 6.72ct


Moissanite Marquise mm size to carat size comparison

10x5mm is about 1.00ct

11x5.5mm is about 1.42ct

12x6mm is about 1.80ct

13x6.5mm is about 2.23ct

14x7mm is about 3.05ct

16x8mm is about 3.68ct


Moissanite Princess mm size to carat size comparison

6.5mm is about 1.70ct

7mm is about 2.10ct

7.5mm is about 2.50ct

8mm is about 3.10ct

8.5mm is about 3.60

9mm is about 4.30ct

10mm is about 5.97ct

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