The carat is the carat weight of the diamond. A one carat diamond is 200 milligrams. Most of the diamonds sold in the industry are under one carat in weight. For that reason, a carat is generally subdivided into “points.” One carat contains 100 points, so if a diamond weighs 3/4 carat, it would be a 75 point diamond. Thus 1 carat = 200 milligrams = 100 points.

The size of the gem should not be misconstrued for the weight of the gem. This could be somewhat equated to such items as cereal boxes wherein the contents are sold by weight, not volume.

In addition, do not misconstrue carats of a diamond with carats of a different gem. Various minerals have different densities. For example a one carat diamond will have a different volume (also known as size) than a one carat ruby. Another confusing aspect of the jewelry industry is that karats that determine the measurement of the purity of gold do not have anything to do with the carats used to measure the weight of a diamond. (Note the difference in spelling: karats; carats.)

Ask the jeweler to weigh the stone while you are watching, if you are not sure of a stone’s carat weight. Make sure there is nothing on the scale before it is weighed. Put the (unmounted) stone on the scale and take the amount of milligrams shown by the scale and divide that number by 200 in order to determine the carat weight of the stone.

Do not just look for the biggest diamond at the best price. You may end up with a stone that has inferior quality of color, clarity and cut. Then the diamond will look cheap when it is compared to other diamonds. Shopping merely for size of a diamond would be like shopping for the largest car without regard for its features and style.

If the size of the diamond is very important to you, make sure you consider the cut, clarity and color as well.