This is the weight of the diamond, measured in carats. Ifyou visit a discount jeweler or shop a department store catalog, you'd think the only thing that matters about a diamond is how many carats it weighs. And indeed, of the 4 C's, carat-weight is the easiest factor to determine, since there is no subjective judgment involved. One carat is 1/5 of a gram (200 milligrams) by weight, and is divided into 100 points. So 3/4 carat is 75 points; 1/2 carat, 50 points; 1/4 carat, 25 points, etc. The chart, below and to the right, shows the approximate size of diamonds of varying carat weights.
Cost-per-carat comparisons and price ranges
To compare the value of different diamonds, it is necessary to know the cost-per-carat. To find this, divide the price of the diamond by the number of carats. E.g., a 77 point (.77 CT) diamond costing $2,000 has a cost-per-carat of $2,597.40. Cost-per-carat comparison is only valid if both diamonds are within the same value size range, according to the chart below.
Diamond values increase with each size range. On average, only one in a million diamonds mined will weigh a carat or more. That is why a one-carat diamond is worth more than twice the value of a half carat (quality factors being equal). The rule is, the larger the diamond, the more rare it is, and the higher the value. The chart shows the break points, where one "point" (1/100th of a carat) can make a significant difference in price ~ typically 10-20% (for example, a .49 CT diamond is worth 10% to 20% less than a .50 CT of equal quality).
Comparing light to full
Another factor making comparison difficult is that the FTC allows jewelers to egally call a diamond a "1/2 carat" starting at .46 CT, and a "one carat" at .96 CT. Technically, diamonds that are .46-.49 CT should be called light halves, and those that are .96-.99 CT, light carats. There is a significant wholesale price difference between a light and a full, so be sure not to compare a light to a full in comparison shopping.
Comparing center stones vs. carat total
Comparing melee (pronounced "melly")
Total cost of mellee in mounting divided by number of points.
is what you can expect to pay for mellee of