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Carats Weight Calculator

This calculator requires the use of Javascript enabled and capable browsers. This script calculates weight conversions between grams of weight and carats, points, kilograms and milligrams. Carats, abbreviated "ct." and spelled with a "c", is a measure of weight used for gemstones. The carat weight was standardized in the 20th century. The United States officially adopted the metric carat in 1913. One carat = .2 grams or 200 milligrams, equal to 1/5 of a gram. Stones are measured to the nearest hundredth of a carat. A hundredth of a carat is also called a point. Thus a .10 carat stone can be called either 10 points, or 1/10 of a carat. Small stones like .05, and .10ct are most often referred to by point designations. The spelling of karat with a "K" is a measure of the purity of a gold alloy, as opposed to stones. A one carat round diamond of average proportions is approximately 6.5mm in diameter. Be aware that this unique relationship of weight and size is different for each family of stones, which can be seen in our Gemstone Carat Weight Estimation Calculator. For example ruby and sapphire gems are both heavier than a diamond; technically, they have a higher specific gravity, so a 1 carat ruby or sapphire is smaller in size than a one carat diamond. We have created a table of Gemstone Characteristics that includes the specific gravity for a vast majority of gemstones. However, I never met a carat I didn't like!

Enter the stone weight in grams and click on Calculate.

Required Data Entry
Grams Weight Value

Calculated Results
Carats Value
Points Value
Milligrams Value
Kilograms Value
Updated 8.15.11

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