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The cut of a diamond refers to its proportions. It is the only element in the 4 Cs that is directly influenced by man as opposed to predetermined by nature. Cut shouldn’t be confused with shape. Diamonds are cut into various shapes depending upon the original form of diamond rough (the uncut diamond). Regardless of which shape is selected, a well-cut diamond will be able to reflect light better and therefore display more brilliance.

Diamonds are cut into numerous facets, which are separate flat surfaces. The exact proportions, angles, and placement of the facets are based on a precise mathematical formula designed to maximize the amount of light reflected through the diamond. The beauty of a diamond increases as more light enters and reflects through it since it will create more sparkle.

The cut is described in percentages relative to the diameter of its girdle. The girdle diameter of each diamond is always considered 100%. For example, if the girdle of a diamond measures 10 millimeters (100%), the table measures 5.8 millimeters, and the total depth measurement is 6.2 millimeters, then the diamond would be described as having a table of 58% and a depth of 62%. The table and depth percentages are the key to determining good proportions.

The ideal proportions for each shape are not the same. Since each shape has its own unique characteristics, the specific guidelines will vary from shape to shape. However, the objective of the ideal cut is always the same - to maximize the beauty of each diamond. Please note that the general guidelines described on this site are based on the Round shape.

Please also keep in mind that even in diamonds, beauty is in the eye of the beholder. Even among diamond experts, opinions will differ due to personal preferences. So while one person might prefer one set of proportions for a particular stone, another person might favor slightly different proportions. Therefore, the best measurement is always what the wearer of the jewelry finds the most beautiful.   

Deep Cut
If a diamond is cut too deep, some light will escape through the opposite side of the pavilion.

Shallow Cut
If a diamond is cut too shallow, light will escape through the pavilion before it can be reflected.

Well Cut
When diamonds are Well-cut, light will reflect from one facet to another and then disperse through the top of the stone. Within the Well-cut classification, there are three sub categories: Ideal, Excellent, and Very Good. This classification system is based on extremely sophisticated tools which are able measure every aspect of a diamond’s proportions. However, it is important to note that in many cases, the differences from one classification to the next are so small that they are indiscernible to the naked eye.

  • Ideal: Considered the best in class, this range of cut is very strict and combines the best in brilliance and fire.
  • Excellent: This range of cut is also considered to create magnificent light display, but is more flexible with regards to percentages. Many experts actually prefer the appearance of Excellent to that of Ideal.
  • Very Good: This range balances precise proportions with price considerations. Many people believe this range of cut offers the best overall value.

The overall cut grade of a diamond is equal to the lowest of the individual scores assigned to that diamond’s particular characteristics. For example, if a diamond’s table percentage falls within the Ideal cut range but its depth percentage is in the Very Good range, the diamond is classified as Very Good.

A diamond’s girdle is the outer edge of the stone. It usually has a frosted appearance and is in many cases, fully polished or even faceted. This characteristic is a based on the cutter’s personal style and doesn’t impact the diamond’s value. The girdle is rated in terms of thickness and is usually described as Extremely Thin, Very Thin, Thin, Medium, Slightly Thick, Thick, Very Thick, or Extremely Thick. It might also be described as a range (such as Thin to Thick). With respect to Girdles, it is best to avoid the extremes. In other words, look for diamond with a girdle that is neither Extremely Thin nor Extremely Thick.

The culet is the bottom point of the diamond and may actually have a very small facet. The culet is described based on its size, generally graded as None or Pointed, Very Small, Small, Medium, Slightly Large, Large, Very Large, and Extremely Large. A smaller culet is more desirable.

The polish of a diamond refers to the finishing or final polishing of the facets. Diamonds are actually ground and polished until they reach their final form, not chipped away as many people believe. A diamond cutter strives to produce facets that shine and are free from polishing imperfections. Polish is generally defined as Poor, Fair, Good, Very Good, or Excellent. It is recommended to purchase diamonds with a polish grading of Good or above.

The symmetry of a diamond describes the alignment and positioning of its facets. When cutting a diamond, the cutter will aim to fashion each facet to be precise and sharp and in the right proportions and angles with respect to the other facets. If facets are joined improperly, the diamond may appear uneven. The symmetry of a diamond is generally defined as Poor, Fair, Good, Very Good, or Excellent. High-quality diamonds will have symmetry of Good or greater