The Connection Between A Diamond’s Diameter And Weight

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One of the most important aspects of a diamond is its carat weight. This particular property of a diamond is obtained shortly after it had been mined, and provides a reading on how much the diamond weighs, as the term suggests. The diamond is essentially weighed in milligrams, which is nothing new to the general population. The milligram weight is then converted into a carat weight. Each 200 milligrams of weight recorded on a diamond grants the particular diamond one carat of weight. A higher carat weight obviously means a significantly higher price. At certain weights, such as one carat (when the diamond reaches a three-digit weight class), the diamond experiences a considerable increase in weight.

The weight of a diamond does not only affect the rock’s price, but also has a significant impact on how the diamond looks. A higher carat weight obviously means a larger diamond – and it is certainly nothing new that the larger a diamond, the happier the receiver of the rock will be. What we would like to discuss in this particular post is the connection that exists between diamond carat weight and the diameter of a diamond.

Diamond Carat Weight And Diameter

While carat weight refers to how much a diamond weighs, diameter is a term that refers to the actual size of a diamond. Diameter itself does not have any effect on how much a diamond will cost, since the carat weight of a diamond is used to determine this particular factor – along with some other quality factors like its cut quality, color grade and clarity rating. This, however, does not mean that the diameter of a diamond has a role to play in the stone’s visible appearance.

DiamondsSince the diameter refers to the size of a diamond – usually referring to the visible part of the diamond – it is an essential factor to take into consideration when deciding which diamond to buy. It is often possible to find a diamond with a larger diameter when you open up your options and explore the market, as compared to a diamond with the exact same carat weight. The cut or shape of a diamond tends to have the most effect on its diameter. For example, while the brilliant round cut is the most popular shape, a lot of people find that they are able to buy a diamond of a similar weight, but with a larger diameter and visible appearance when they rather opt for a different shape, such as the emerald cut.

When it comes to the brilliant round cut diamond, the following connections have been established:

  • A carat weight of 0.18 to 0.22 carats has a diameter that ranges from 3.65 millimeters to 3.90 millimeters.
  • A carat weight of 0.50 to 0.68 carats has a diameter that ranges from 5.15 millimeters to 5.65 millimeters.
  • A carat weight of one carat has a diameter between 6.40 millimeters and 6.50 millimeters.
  • A carat weight of two carats has a diameter that ranges from 8.05 millimeters to 8.10 millimeters.
  • A carat weight of five carats has a diameter that ranges from 10.9 millimeters to 11.1 millimeters.


While diamond weight is often considered the most important aspect of a diamond, contributing to both size and price, individuals interested in buying a diamond should not disregard diamond diameter. When buying on a budget, opting for certain cuts can add a larger diameter and visible table when a lower carat weight is needed. In this post, we discussed how carat weight and diameter is connected, and how you can use this connection to your advantage.


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Kevin Lee is a former tech advisor who cut his teeth in Silicon Valley. He now spends his time sharing his passion for investing in diamonds and jewelry. You can reach Kevin for any comments by using the contact form on this site. Don't forget to sign up for his free "Investing 101 Guide" by clicking on the button at the top right of this website.