Out of the four C's, this is one of the easier characteristics to comprehend. The 'carat' simply refers to the weight of the diamond. Nevertheless, a large carat does not always equate to a big diamond in terms of size, so it is worth bearing this in mind, as some shapes can look larger than others even though they have the exact carat weight. The Marquise diamond, for example, is well known as being a diamond that optimizes its carat weight to give a bigger appearance.
Another point to keep in mind is that the term 'karat' is used in jewelry to represent the purity of gold. The two are not to be confused. Carat, with a C, is a unit of weight, and it will often be written as 'ct'. This unit of weight was accepted in 1914 in the UK as the official diamond measurement, and it is now the standardized worldwide measurement. Essentially, 200 milligrams equates to one carat.
The carat weight is one of the four key factors that are considered when determining the quality of a diamond, with the others being clarity, colour, and cut. Generally, the more expensive diamonds are the heavier ones. This is often because they are quite scarce. You do need to consider the shape and cut of the diamond carefully to get a full picture regarding the diamond's size.
Carat is denoted by ‘ct’
1 carat = 0.2 gram
5 carat = 1.0 gram
The term 'carat' is derived from the name of the locust or carob tree, which can be found in the Mediterranean lands. In the past, traders used the dried seeds of this tree as a unit of weight for gems.
If you want to maximize monetary value when purchasing a diamond, it is a good idea to opt for a carat weight that falls just below one of the popular weights, such as 1/2 ct and 1 ct. Your diamond will fall just shy of one of the more common weights, and thus you can expect a reduced price. Oversizes can trade at five to 15 percent premiums over similar quality straight sizes.
Oversizes are: 5.50+, 3.50+, 2.50+, 1.75-1.99, 1.30-1.49, 0.96-0.99, 0.80-0.89, and 0.60-0.69