Carat is the first of the four C’s and refers to the size or carat weight of a finished polished diamond.
When diamonds are mined, smaller crystals are discovered more frequently than larger crystals, therefore making larger diamonds rarer and much more valuable.
Diamond prices rise exponentially with carat weight, a 2 carat diamond of a given quality is always worth more than two 1 carat diamonds of the same quality.
Of the 4 C’s carat weight is considered to be one of the most significant factors in determining the value of a diamond.

Carat weight is divided into points, a unit of weight used only for diamonds.
1 point = 1/100 (0.01) carat
25 points = 25/100 (0.25) also known as quarter of a carat
50 points = 50/100 (0.50) also known as half a carat
75 points = 75/100 (0.75) also known as three quarters of a carat
100 points = 1.00carat

The size of a finished diamond is directly related to its carat weight. However the actual dimensions are entirely dependent
upon its proportions.

carat weight and average diameters