What is Carat in Diamond

A carat is a metric measurement that is equivalent to slightly more than seven thousandths (0.007) of one ounce. Diamond weights are measured with the accuracy of a thousandth of a carat but are given a weight that is rounded to the nearest hundredth. Diamonds weighing over one carat are designated as a decimal number up to the hundredths, such as "1.23 carats." Such a weight would be expressed as "one carat and twenty three points." A diamond weighing less than one carat is also represented as a decimal, such as 0.72, in which case it would be said to weigh "seventy two points."

Though a diamond's value is determined by its weight in carats, a two carat diamond would cost more than two times the amount that an equivalent one carat diamond would cost.
Diamonds with adequate quality to be used in jewelry are rare finds, with larger diamonds being even less commonly discovered than smaller ones. As economics demonstrates, the more limited the supply a valuable product, the higher cost it will claim. As such, there is no defined measurable rate representing a diamond's cost per carat. Rather, larger diamonds fetch an exponentially higher price per carat than the more common smaller ones.