What unit are diamonds always measured in?

• A. Millimeters.
• B. Carats.
• C. Inches.
• D. Micrometers.

Answer: (A)

Diamonds are described by their physical size using millimeters. The diameter (for round stones) or the length and width (for shapes like princess or emerald cuts) are stated in millimeters because these dimensions define the stone’s proportions and how it will appear when set. Carat is a separate measure that denotes weight, not size, so it’s used alongside millimeter measurements but does not replace them. Inches and micrometers aren’t the standard units for describing a diamond’s size in the trade. So the unit most consistently used to describe the diamond’s size is millimeters.