For many diamond lovers, size matters!
Carat denotes the weight of the diamond, i.e., its size. Carat is abbreviated as “ct” and has nothing to do with the carat value of gold (which is a measurement of how much gold is actually in a gold piece).
A one-carat diamond corresponds to 0.2 grams. 

Size is the most obvious factor in determining the value of a diamond. Size is also the easiest factor to assess; the diamond is placed on a very accurate set of scales. If you wish to throw in some “diamond speak”, you may use terms such as “35 points”. A carat is divided into 100 points. In other words, a diamond weighing 0.35 carats is a thirty-five pointer, while one weighing 0.03 is a three-pointer.

In very rough terms, you can say that a round diamond with a surface of 5 mm as seen from above is 0.5 carats and that 6.5 mm equates to 1 carat. The larger the diamond, the rarer – and, therefore, more expensive – it is. Two 0.50 ct diamonds are cheaper than one 1 ct diamond, even though they make 1 ct together.

Those who would like the most possible diamond for their money and do not care about an even carat size, could look at diamonds just below one whole or one-half carat, as the uneven weight comes at a slightly more favourable price.