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How to Count Diamond Carats

The carat system first began when gem merchants weighed diamonds against carob seeds due to the fact that the seeds uniform size made them a standard for weights and measures. In the 1940s, the Gemological Institute of America (GIA) developed a universally recognized diamond and gemstone grading system to measure carat weight. Diamond carats are counted in a manner similar to dollars and cents. In other words, 1 carat equals 100 points. Decimals also apply in counting carats. For example, 125 points would equal 1.25 carats. A diamond's dimensions and cut grade are also key elements in determining its overall carat value.

Things You'll Need

Diamond
Scale
Size chart

Instructions

- 1
  Weigh each diamond using an electronic micro-balance gemstone scale. This can be done by a GIA-certified jeweler, appraiser or gemologist.
- 2
  Convert the carat reading on the scale to determine the diamond's point value. One carat is equal to 100 points. So if the reading on the scale is 1.5 carats, that would be equal to 150 points. If the diamond weighs less than 1 carat, as most marketed diamonds do, the point value would be less than 100. A quarter carat, for example, would be worth 25 points.
- 3
  Compare the carat weight and point value with its corresponding measurements on a diamond carat size chart to determine its base carat value. Diamonds are customarily priced by carat. However, other factors, such as color, cut and clarity may also affect the price.

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