Diamond Carat Weight & How to Calculate it in Grams

Sharif Khan
Sharif Khan
Last Updated    EST 

A carat is the unit of weight used to measure a diamond. The word "carat" has its roots in Greek. In ancient times, carob seeds were considered to have consistent mass. Hence, they became a comparative measure for facilitating the trade of diamonds.

Carat has remained a relative measure for diamonds for a long time. Its net weight varied from place to place until 1907 when it was defined and standardized. Today, one carat equals 0.2 grams, approximately the size of a paperclip. A carat is further divided into one hundred points. When shopping for a diamond, the most common term you will hear from jewelers is "carat," which indicates the size of the diamond, along with many other quality factors and shapes.


  • One carat equals 0.2 grams. 
  • The bigger the carat weight, the rare the stone. Prices multiply significantly as carat weight increases due to its rarity.
  • Total carat weight is not the same as carat weight. 

Calculating Carat Weight & Prices

Given that 1 carat equal to 0.2 grams, if we were to calculate the weight of a 0.8 carats diamond, the weight in grams would be = 0.8 carats * 0.2 grams/carat weight in grams = 0.16 grams.

The larger the carat weight of a diamond, the higher its price per carat -- the bigger the diamond, the rarer it becomes, which adds to its price. Two engagement rings, each having a diamond weighing one carat, may cost $5,000, whereas one with a 2-carat diamond may cost $20,000. A bigger diamond can be considerably more expensive than a smaller one. For example, a Round SI1 F Very Good Cut 1ct will cost $4,800, while a similar 2ct will cost $15,000 (the per carat weight of the latter becomes $7,500). At the same time, many other factors determine the price of a diamond, including colorclarity, and cut.

James Allen Diamonds

The carat weight of a diamond can be determined by measuring—table up—the diamond in millimeters across the widest and narrowest points, apart from the depth or height. Once these measurements are taken, they can be put into any online diamond carat weight calculator. Afterward, you will be required to specify the shape of your diamond, following which you will be able to see its exact weight in carats.

Since every carat is divided into one hundred points, you will find diamonds in different ranges, e.g., 1.25 or 0.25 carats. Imagine a dollar in your mind – 1.25 carats would be like one dollar plus a quarter, or 0.25 carats would be like a quarter of a dollar.

Diamond Carat Sizes Chart

Total Carat Weight

Many diamond sets or rings will feature more than one diamond. As a result, the cumulative weight of all diamonds will be displayed in the item's description. In such cases, you will see the total carat weight (TCW/TW), which represents the combined weight of all the diamonds in that piece of jewelry. It's important to note that TCW/TW is not equivalent to the carat weight of a single diamond. Instead, it signifies the total weight of all the diamonds mounted in the jewelry.

Diamond Cheat Sheet Blue Nile

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