What is a Carat?

wiseGEEK Writer

A carat is a type of measurement used to describe the mass or weight of a gem. The term was initially applied to diamonds only. Now it applies to most precious and semi-precious stones.

The larger the carat weight of a cut diamond, the more rare and expensive it is.
The larger the carat weight of a cut diamond, the more rare and expensive it is.

Some confusion exists in the very word carat, since gold is also evaluated in carats or Karats. Karat is the more traditional spelling when referring to gold and does not apply to mass. Instead, gold is classed by purity. Twenty-four Karat gold, for example, has the greatest purity, while 10 Karat gold has the least.


When the term carat refers to a gem’s mass, it does not refer to the quality of the gem. Evaluating cut, clarity, and color, as well as carat, is the best way to select a gem. A stone's size or weight can be measured on the metric scale. One carat is the equivalent of 0.2 grams.

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Carats can apply to precious or semi-precious stones.
Carats can apply to precious or semi-precious stones.

When a jewelry item has small diamond chips in it, the measurement may evaluate total carat weight (tcw), rather than giving specific measurements of each chip. Small chips are far less expensive than single larger gems because they are more common.

Most uncut diamonds are considerably larger than cut varieties available through retailers. Uncut diamonds are full of flaws and must be cut to achieve the best looking diamonds. The larger the carat weight of a cut diamond, the more rare and expensive it is. Diamond chips are not particularly expensive, but retailers often employ a listing of tcw to make the article of jewelry seem more impressive. One will notice however, that jewelry including small diamond chips tends to be offered at far lower prices than jewelry with single large stones.

In fact, the value of a diamond or other gem increases dramatically as the stone size increases in weight. A half carat diamond may cost about a fourth the price of a carat diamond. Price increase is due to the rarity of unflawed larger stones.

Jewelers are quick to assure potential customers that size matters. However, the cut and clarity of diamond, along with its setting, may make a small diamond seem larger. A one-carat diamond that is full of flaws may not be as impressive as a half-carat diamond that is close to perfect. Each flaw decreases the ability of the stone to reflect light, so flawed gems are less sparkly.

A carat is used to describe the mass or weight of a diamond or other gem.
A carat is used to describe the mass or weight of a diamond or other gem.

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Discussion Comments


@ PelesTears- If you are on a budget, and size does matter, look for a diamond with at least a medium blue fluorescence. A medium fluorescence can mask some of the color of a diamond. The fluorescence will make a diamond appear about one to two color grades whiter. A diamond with a color grade of J will appear to be an H or I.

You should also stick with a brilliant cut diamond, and a smaller table. An emerald cut 1 carat stone has a very large table, so you will see all of the color and flaws trapped in the stone. All of these characteristic combinations will allow you to purchase a larger stone with a very good to excellent cut for a cheaper price. The diamond will look great, but not cost you an arm and a leg.


The article is right that size does not always matter. A third carat diamond that has excellent cut, good clarity, and whiter color will look much nicer than a half or three-quarter carat diamond ring that is of poor quality. A diamond with a poor cut will not reflect light well, creating dark spots on the stone as the light passes straight through. Large flaws will also disrupt the refraction of the light, affecting the stone’s sparkle.

When I shopped for my fiancée’s ring (on a student's budget) I was able to find an excellent diamond for a very reasonable price. I bought a 0.36 carat diamond that showed more light and fire than a comparable priced half carat diamond. When viewed in the light, the diamond actually looked larger than the larger diamonds of the same price I viewed, mostly because it shone brighter.

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