Hello, I'm an expert in gemology with a focus on diamonds. When it comes to the size of a diamond, "carat" is a unit of weight, not size. However, the weight of a diamond is directly related to its size. A one-carat diamond is equal to 0.2 grams or 200 milligrams.

The size of a diamond in terms of dimensions can vary greatly depending on the cut. For a round brilliant cut, which is the most common, a one-carat diamond typically measures about 6.5mm in diameter. However, this can vary due to the depth and table percentage of the cut. For example, a cushion cut might have different dimensions even at the same carat weight.

To give you a more visual understanding, if you were to line up 100 one-carat diamonds, they would weigh exactly 20 grams, which is the weight of one carat multiplied by 100.

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As you can see above, the size of a 1 carat diamond is approximately 6.5mm (based on the assumption that the stone is cut to ideal proportions). On the other hand, the size of a .5 carat diamond is approximately 5.2mm. Even though the carat weight is 50% of a 1 carat stone, it doesn't face up twice as small!read more >>