Princess Cut Diamond

The princess cut is the second most popular cut shape for diamonds, next to a round brilliant.The Princess cut diamond is a "fancy" (i.e. non-round shaped) brilliant cut - and is either exactly square or slightly rectangular when viewed from directly above the crown.

Princess cut diamonds also tend to have a slightly lower price-per-carat than round cut diamonds. This is because the four sided pyramid shape of the princess cut diamond is similar to one half of the octahedron rough stone from which a princess diamond is cut. This similarity allows two equally sized princess cut diamonds to be cut from the same rough stone with relatively little waste (roughly 60% of the weight of the original rough stone is retained after cutting). The greater efficiency, or yield, translates to a lower price.

Carat for carat, the crown surface area of a princess cut is about 10% less than a same-weight round diamond. However, the corner to corner measure of a princess cut is typically 15% greater than the diameter of a same-weight round diamond, creating the illusion of greater size.
Princess Cut Diamond LW Ratios

The princess is traditionally a square cut (four sides of equal length). However, many princess cut diamonds are slightly rectangular, though this is often hard to detect. All other things being equal, the more rectangular a princess cut diamond, the lower the price. Many buyers actually prefer a slightly rectangular princess cut; it's all about finding what is most pleasing to you. Any length to width ratio of 1.05 or less will appear square to the naked eye. If the princess will be set with side diamonds, a length to width of 1.05 - 1.08 may still look square, as the side diamonds will create the illusion of greater width in the center stone.

A princess cut diamond should always be set with prongs that protect the four corners (the most likely location for chipping). Because these corners were once near the outer edge of the rough stone, flaws such as naturals, extra facets, and other inclusions may be located here. Since the corners are covered by the prongs, these flaws will be invisible once the diamond is set. The only remaining concern would be if the flaws are significant enough to affect the stability of the diamond (this is extremely rare, however). Most other square cuts (such as emerald, asscher, and radiant) have cropped corners.