Cut refers to the angles and proportions skilled craftsmen create in transforming rough diamonds. The cut of a diamond meaning the roundness, the depth and width, the uniformity  of its facets — establish a diamond's brilliancy. Many gemologists consider the factor of cut to be the most important feature of diamonds because even when a diamond has the perfect color and Clarity grades, if it was  poorly cut it will have dulled brilliance.

The width and depth have the most impact on how light travels inside the diamond, and how it exits in the appearance of radiance.

The diamond's proportions, specifically the depth compared to the diameter, and the diameter of the table compared to the diameter of the diamond, establish how well light will reflect and travel through the diamond.

Cut is far more complicated than the other C's and depends on a variety of factors. Ideal cuts are usually much more expensive than the others. It all boils down to the quality of the cut, but lots of cases have to be studied before making a final decision.

Finally a diamond's per carat price goes up when it is a better cut or better color grade. The same way that grading measures the level of colorlessness and the same way that clarity grading measures the degree of flawlessness, cut grading measures the degree of a diamond's brilliancy.

The utmost important characteristic of a high quality diamond and the real beauty of diamonds, is the magnificence of its brilliance. Cut meaning the proper proportions and fine finish of a diamond are what cause the diamonds brilliancy and radiance – the light returned to the diamond viewers' eye. The cut of a diamond is influential on the diamonds price by close to 25% yet it is the least understood by customers purchasing diamonds.

In every diamonds description there are two terms that people confuse, shape and cut. Shapes, define the diamonds overall appearance such as round or princess, specify the overall style of the specific diamond. The cut of a diamond however, describes the individual diamonds shape proportions and finish, each diamond shape has its distinctive proportion and finish parameters.

Table - is what defines the largest and top-most facet on the diamond's crown. The table percentage is the value which explains how the diameter of the table compares to the diameter of the entire diamond. So, for example a diamond that has a table of 53% means that the table is 53% as wide as the diamond's outline. For a round diamond, gemologists evaluate table percentage by dividing the diameter of the table and comparing it to the girdle diameter. For the other diamond shapes, table percentage is calculated by dividing the width of the table, at the widest measurement of the diamond, and comparing it to the width of the entire diamond. The Table measurements are subtleties which differ very slightly and should not be taken out of proportion in selecting a diamond.

TOTAL DEPTH AND TOTAL DEPTH PERCENTAGE

Every diamond grade description contains information about a diamond's total depth and its total depth percentage. Total depth percentage is calculated by dividing the diamonds total depth by the girdles diameter.

Proportions, , the pragmatic facts and levels of angle measurements and the percentage of measurements, measure the detailed characteristics of every diamond. In round diamonds measurements are calculated in the relation to the diamonds average diameter where a table measurement of 55% and a total depth measurement of 60% are calculation stating their percentage of the averaged diameter of the diamond. Measurements for stretched out diamond shapes such as ovals are calculated only as a percentage of the diamonds width. The degrees are used to measure the angle of the crown and pavilion of the diamond in association to the level surface of the girdle.

The - finest cut diamonds return light back to the viewers eye in a uniform manner when they are in a face-up position. Here no dark areas are possible. Dark areas are caused by poor cut. When diamonds are cut well, light enters from the table and continues to the pavilion where it reflects from one side of the diamond to the other increasing by the mirror-like facets as it travels - before reflecting back out of the top of the diamonds table to the observer's eye. This brilliance that comes from the very heart of the diamond is known as brilliance.

Finish is an interpretive calculation of the quality of the polish of a diamonds outside surface and also the symmetry. Diamond shape affects this grade because each shape is graded by its own cut characteristics and its proportions and finish. Both factors the proportions and the finish are measured in judgment of the overall cut grade assigned to a diamond.
is an interpretive observation of the quality of both the polish of a diamonds outside surface and its symmetry, the relationship of one cutting feature to another, the alliance of the diamond. Each diamond shape is graded by its cut characteristics and its proportions and finish. Both factors the proportions and the finish are measured in judgment of the overall cut grade assigned to a diamond.

Polish - defines imperfections on the surface of the diamond not considerable enough to have an effect on clarity.

Symmetry - defines the differences in a diamond's symmetry. Small variations can include misaligned facets or facets that fail to direct exactly towards the girdle this phenomena is completely unnoticeable to the unaided eye. Symmetry problems are found in diamonds graded fair or poorer.

Cut defines the quality of the optical properties of diamond as those optical properties relate to the light we perceive in viewing a diamond, to put it simple the magnificence of a diamond is, really, just the magnificence of light. As soon as a diamonds color and clarity standards are in gem grade meaning that no visible inclusions and no apparent coloring appear the visual and optical points become most importantly needed for the diamonds magnificence.

As you have read diamond cut grading has several points for thought. Unlike color grading which measures the range from colorless to yellowish and is relatively easy to understand, and clarity grading rates the location, nature and dimension of inclusions, cut is far more complex and helps determine the amount of light that will be dispersed that is why it is harder for the mind to “portrait” and therefore, even though it is the most important factor in a diamonds beauty it is the least understood element.