Carat Weight

 

Diamonds and other gemstones are weighed in metric carats: one carat is equal to 0.2 grams, about the same weight as a paperclip. (Don't confuse carat with karat, as in 18 Karat Gold, which refers to gold purity.)

Just as a dollar is divided into 100 pennies, a carat is divided into 100 points.  For example, a 50-point diamond weighs 0.50 carats.  But two diamonds of equal weight can have very different values depending on the other members of the Four C's: clarity, color and cut. 

 

Because even a fraction of a carat can make a considerable difference in cost, precision is crucial.  In the diamond industry, weight is often measured to the hundred thousandths of a carat, and rounded to a hundredth of a carat.  Diamond weights greater than one carat are expressed in carats and decimals.  (For instance, a 1.08 ct. stone would be described as "one point oh eight carats," or "one oh eight".)