Diamond size is measured in carat weight (ct). One metric carat is equivalent to 200 milligrams.
The chart below illustrates the relative size of popular carat weights for round-cut diamonds. Note that a 2.00ct diamond does not appear to be twice the size of a 1.00ct diamond when viewed from the top.
Note: Use this chart as a relative guide only.
Actual diamond sizes will vary.
Carat weight refers to a single diamond, and carat total weight (ct tw) refers to the weight of all diamonds in a particular piece. For example, diamond-stud earrings that have 1.00ct tw actually contain two diamonds that weigh approximately .50ct apiece.
Bigger is not necessarily better in terms of a diamond’s value. The brilliance and beauty of a diamond also lies in its more subtle properties of cut, clarity and color.