A one-carat diamond is usually around 6.4 to 6.5mm wide, which is the perfect size for the center stone—not too big, not too small. It’s one of the more common sizes of diamond, due to its wide availability and generally lower price point, however, this can be affected by a diamond’s other qualities, namely its cut, color, and clarity.
In terms of diamond price and size, the cost isn’t linear. A two-carat diamond isn’t the price of a one-carat diamond, as prices ascend exponentially. Take these two diamonds. The first is a beautiful 1.00 ct D VS1 Round Cut Loose Diamond currently priced at $9,390.