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Diamond Carat Weight

For many people, bigger is better when it comes to their diamond jewelry. This is why, when you come to Joseph Jewelry’s custom jewelry design business in Seattle and Bellevue, it is good to be familiar with the concept of carat weight.

What is a Carat?

A carat, not to be confused with a karat (a measurement that denotes the purity of gold), is a unit of measurement used to describe the weight of diamonds and other gemstones. While carats have regularly been used to measure diamonds since the 1540’s, early carat weights had no clear cut definition agreed upon between countries. Since 1913, however, the international standard is that one carat is equal to 200 milligrams, or 1/5th of a gram. Most jewelers will round diamond weights to ¼ or a carat, and pieces with multiple diamonds may have numbers listed as total carat weight (CTW), which is the total weight of all the diamonds in the setting.

One theory states the term "carat" comes from the Greek word keration, or "fruit of the carob" – i.e., a carob seed. The story says that ancient gem traders discovered that carob seeds were remarkably consistent in weight, and therefore used as a counterweight when weighing diamonds. A diamond was put on one part of the scale, carob seeds on the other, with one carob equaling one carat.

On grading reports, carat weight is reflected as a percentage of 100, with 100 points being equal to 1 carat. This is usually listed on certifications in decimal format, so:

1 carat = 100 points = 1.0

¾ carat = 75 points = 0.75

Carat vs. Weight vs. Size

Weight does not equal size. Because of differences in depth and cut, two diamonds with identical diameters may in fact be two completely different sizes. Therefore, it is possible to buy a diamond that looks bigger than another one but that may actually have a smaller carat weight. When purchasing a diamond, consider not only the carat weight but also the length vs. width (therefore taking into account the depth of the stone) as well as the surface area of the face of the diamond – the part that will actually show when the stone is set into an engagement ring.

What Carat is Right For Me?

Carat weight is best place to control the price of your stone. As carat weight increases, the price of a diamond increases exponentially. Therefore, a 1.0 carat diamond is not simply double the price of a .5 carat diamond. Assuming all the other characteristics are the same, it actually may be more than two or three times the price simply because larger diamonds are much rarer than smaller ones.

For the best value and beauty in a diamond, go ask your jeweler for a stone with VS1 to VS2 in clarity, F to I in color, get the best cut possible, then use the carat weight of the diamond to leverage the price. Always remember that a larger stone rendered lifeless because of a poor cut, excessive inclusions or murky color will be much less impressive than a smaller carat stone with an excellent cut, clarity, and color.