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Diamond Carat Weight


Diamond carat weight is a metric measure of Diamond weight. 1 Carat is equivalent to 0.20 grams.  In the same way that a pound is divided into 100 pennies, one carat is divided into 100 points.  A Diamond weighing half a carat will also be described as being 0.50cts in weight.  The carat weight of a Diamond is one of the determining attributes defining the value of a Diamond. 

Use the application below to change the carat weight, diamond shape and hand colour. Further information is available in the menu to the left of the application. 

Please note that if you are ordering our Swarovski Crystal alternative to our natural Diamonds, we use perfectly faceted replica stones relating to the same diameter size chosen. In our online menu, you will see the relative Diamond weight for the size chosen. 

A note on carat weight and Diamond size

Diamond carat weight should not be confused with the physical Diamond size. It stands to reason that as carat weight increases, so does the physical size of the Diamond. For the relationship between Diamond carat weight and physical size alongside shape, see our interactive tool featured below.


The origin of Diamond carat weight

The word 'Carat' originates from a Greek word for the 'Carab' plant—seeds from which were used as a consistent weight measure. Regular sized Carob seeds consistently weigh close to 1 carat each with only a slight variation. This consistency contributed to their application as a reliable measure of weight.


Carob seeds, were once used with balance scales 
 to help determine diamond carat weight  


Expressions of Diamond carat weight

Metric carat weight for Diamonds and gemstones was made legal at the introduction of the Weights and Measures Act of 1963. The Metric Carat weighs 200 milligrams, 0.20 grams or 1/5 metric gram. Alternative expressions for carat weight include. 

Decimal Weight - Conventionally carat weight is expressed to two decimal places for commercial transactions. A half carat Diamond will, therefore, weigh 0.50cts.

Fractional Carat Weight - We often express carat weight in fractions. 1/4 carat, for example, represents 0.25cts or a quarter of a carat. 

Points - Used to express Diamond weight below a full carat. One carat is divided into 100 points. Half a carat in weight would be expressed as 50 points. A quarter of a carat would be expressed as 25 points. 

Grains - A measure of weight, usually associated with pears. For Diamonds, a grain represents a quarter of a carat in weight or 0.25cts. Diamonds falling close to 0.25cts or multiples of 0.25ct weights are called grainers. 0.23 - 0.26cts (one grainers) 0.47 - 0.56cts (two grainers) 0.72 - 0.76cts (three grainers) and so on.

Melee - Refers to small groups of Diamond sizes. 

Number of Diamonds per carat - an expression of Diamond approximate Diamond size relating to the number of Diamonds that would make up a carat in any given size bracket. For example, 6pc (six per carat) Diamonds are individually 0.16cts in weight. (6 x 0.16cts = 1.00ct) A parcel of Diamonds weighing around 0.15 - 0.16cts per Diamond would be described as a parcel of 6pc or 6 per carat.