Moissanite Conversion Chart

Understanding moissanite sizes can be confusing, especially since carat weight is traditionally used for diamonds—while moissanite is measured mainly by millimeter size. This Moissanite MM to Carat Conversion Chart provides a clear, accurate comparison to help you visualize how each stone size looks and how it translates into approximate diamond-equivalent carat weight.

Designed for all popular shapes, including Round, Oval, Emerald, Pear, Cushion, Princess, Radiant, Marquise, Heart, and more, this chart lets you quickly compare sizes side-by-side. Whether you’re choosing a center stone, matching side stones, or helping customers select the perfect size, this guide makes the process simple and reliable.

The chart includes:

Exact millimeter dimensions for each moissanite shape
Diamond-equivalent carat values for easy comparison
Consistent proportions based on standard cutting styles
A helpful reference for jewelers, retailers, and buyers

Perfect for product listings, jewelry design consultations, or customer education, this conversion chart ensures clarity and confidence when selecting moissanite of any shape.

Round Moissanite Conversion Chart

Hearts & Arrows Round Cut

MM Width	Approximate Carat Weight
4.0mm	0.25ctw
4.5mm	0.33ctw
5.0mm	0.50ctw
5.5mm	0.65ctw
6.0mm	0.80ctw
6.5mm	1.00ctw
7.0mm	1.20ctw
7.5mm	1.50ctw
8.0mm	1.90ctw
8.25mm	2.00ctw
8.5mm	2.20ctw
9.0mm	2.75ctw
9.5mm	3.25ctw

Old European Round Cut

MM Width	Approximate Carat Weight
5.0mm	0.50ctw
5.5mm	0.60ctw
6.0mm	0.80ctw
6.5mm	1.00ctw
7.0mm	1.25ctw
7.5mm	1.60ctw
8.0mm	1.90ctw
8.5mm	2.40ctw
9.0mm	2.90ctw
9.5mm	3.50ctw
10mm	3.90ctw

Round Rose Cut

MM Width	Approximate Carat Weight
6.5mm	0.60ctw
7.0mm	0.85ctw
7.5mm	1.10ctw
8.0mm	1.40ctw
8.5mm	1.80ctw
9mm	2.00ctw

Radiant Cut Moissanite Conversion Chart

MM Width	Approximate Carat Weight
7×5mm	1.20ctw
7.5×5mm	1.30ctw
8×5.5mm	1.40ctw
8×6mm	1.80ctw
8.5×6mm	1.90ctw
9×6.5mm	2.40ctw
9×7mm	2.75ctw
9.5×7mm	2.90ctw
10×7.5mm	3.10ctw
10×8mm	3.90ctw
11×8mm	4.80ctw
12×9mm	6.00ctw

Princess Cut Moissanite Conversion Chart

MM Width	Approximate Carat Weight
6×6mm	1.20ctw
6.5×6.5mm	1.30ctw
7×7mm	1.90ctw
7.5×7.5mm	2.10ctw
8×8mm	2.25ctw

Pear Cut Moissanite Conversion Chart

MM Width	Approximate Carat Weight
8×5mm	1.00ctw
9×6mm	1.50ctw
10×7mm	2.10ctw
11×7.5mm	2.70ctw
12×8mm	3.20ctw
13×9mm	4.70ctw
15×10mm	6.60ctw

Oval Cut Moissanite Conversion Chart

MM Width	Approximate Carat Weight
5×3mm	0.30ctw
6×4mm	0.55ctw
7×5mm	0.90ctw
8×5.5mm	1.10ctw
8×6mm	1.40ctw
8.5×6mm	1.50ctw
9×6mm	1.80ctw
9×6.5mm	1.90ctw
9×7mm	2.00ctw
9.5×7mm	2.20ctw
10×7mm	2.30ctw
10×7.5mm	2.60ctw
10×8mm	3.00ctw
10.5×8mm	3.10ctw
12×8mm	3.50ctw
14×10mm	6.00ctw

Marquise Cut Moissanite Conversion Chart

MM Width	Approximate Carat Weight
9×4.5mm	0.75ctw
10×5mm	1.00ctw
11×5.5mm	1.30ctw
12×6mm	1.60ctw
13×6.5mm	2.10ctw
14×7mm	2.90ctw

Emerald Cut Moissanite Conversion Chart

MM Width	Approximate Carat Weight
7×5mm	1.00ctw
7.5×5mm	1.15ctw
8×5.5mm	1.35ctw
8×6mm	1.75ctw
8.5×6mm	1.80ctw
9×6.5mm	2.20ctw
9×7mm	2.50ctw
9.5×7mm	2.60ctw
10×7.5mm	3.10ctw
10×8mm	3.50ctw
11×8mm	4.10ctw
11×9mm	4.90ctw
12×9mm	6.00ctw

Cushion Cut Moissanite Conversion Chart

MM Width	Approximate Carat Weight
4×4mm	0.35ctw
4.5×4.5mm	0.50ctw
5×5mm	0.60ctw
5.5×5.5mm	0.75ctw
6×6mm	1.00ctw
6.5×6.5mm	1.30ctw
7×7mm	1.60ctw
7.5×7.5mm	2.00ctw
8×8mm	2.40ctw
8.5×8.5mm	2.75ctw
9×9mm	3.25ctw
9.5×9.5mm	4.25ctw
10×10mm	5.00ctw