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A Guide to Diamond Carat Weight


Diamond carat weight is a measure of the size or mass of a diamond. It is one of the four essential factors determining a diamond's quality, along with cut, color, and clarity, typically referred to as the 4Cs. The term carat weight began with carob seeds when early gem traders used these small, uniform seeds as counterweights in their balance scales. 


This Graff Guide provides a comprehensive analysis of diamond carat weight, including its definition, the importance of carat weight in selecting a diamond, and an overview of the carat weight scale.


What is a diamond carat?


Carat is the unit of measurement used to describe a diamond’s weight and is equal to 200 milligrams or 0.2 grams. Every Graff diamond is a true masterpiece, from perfectly proportioned stones of less than one carat to extraordinary gems weighing over 100 carats, such as the


What is the diamond carat weight scale?


The diamond carat weight scale is used to measure the weight of a diamond, with each carat consisting of 100 points. For example, a 0.5 carat diamond is equivalent to 50 points, while a 1 carat diamond is equivalent to 100 points. Carat weight can vary significantly from fractions of a carat to hundreds of carats. 


Less than 0.5 carats: Diamonds of 0.5 carats and less are typically used as accent stones in jewelry; for example, a 0.25 carat diamond may be used as a side stone in an engagement ring. 

From 0.5 to 3 carats: This carat range is a popular size for engagement rings and other fine jewelry pieces. A 1 carat diamond is often used as a benchmark for the centre stone within an engagement ring. 

From 5 carats upwards: Diamonds weighing 5 carats and above are considered rare and are often incorporated into high jewelry pieces. 

Image shows diamond carat chart, diamond carat weights ranging from 0.75cts to 6.00cts

An overview of the Gemological Institute of America (GIA) diamond carat weight grading system 


Established in 1931, the GIA is a public-benefit, non-profit institute renowned for its gemological research. The GIA protects consumers through analysis, education, and gem grading and sets global quality standards. The GIA independently verifies the origins of many of Graff’s diamonds and gemstones.


The GIA developed a standardized carat weight grading system to ensure consistency and accuracy in diamond grading. The system ranges from 0.01 to 10 carats, with each category representing a specific range of weights: 


Melee: Less than 0.18 carats

Small diamonds: 0.18 to 0.99 carats

Medium diamonds: 1.00 to 1.99 carats

Large diamonds: 2.00 to 2.99 carats

Very large diamonds: 3.00 to 3.99 carats

Exceptionally large diamonds: 4.00 to 4.99 carats

Rare diamonds: 5.00 to 10.00 carats


The carat weight of a diamond is directly related to its size; however, diamond carat weight alone does not define a stone's beauty, and each of the 4Cs must also be taken into consideration. The larger the carat weight, the larger the diamond; however, it is also essential to consider a diamond’s cut, as this can also impact its overall appearance. 

Frequently Asked Questions

Carat weight is highly subjective and dependent upon personal preference. When purchasing a diamond, it is also essential to consider the stone’s cut, clarity and color, as these will all determine its overall beauty. 

A carat is a unit of measurement used to weigh diamonds and other precious stones. One carat equals 200 milligrams or 0.007 ounces. This means that a diamond weighing one carat has a mass of 200 milligrams, regardless of its shape or size.

It is impossible to determine a diamond's carat weight by sight alone. Carat weight is calculated by placing a diamond or gemstone on a sensitive scale and measuring the small increments of weight in which these gems are measured. 

A true family business, Graff is unique in the world of diamonds. As custodians of some of the world’s rarest and most celebrated stones, the incredible collection of precious gems within its vaults is a testament to the expertise, experience and pioneering spirit of the House, whose reputation for diamond excellence is incomparable.  


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