Question: how many mm is a 2 ct diamond?
Answer: Even though the carat weight is 50% of a 1 carat stone, it doesn't face up twice as small! Likewise, the physical size of a 2 carat diamond (8.2mm diameter) isn't twice as big as that of a 1 carat diamond (6.5mm diameter). Hopefully, this clears up the misunderstanding of carat weight and actual sizes.