Cut is often decided by the original shape of the rough stone, location of the inclusions and flaws to be eliminated, the preservation of the weight, popularity of shapes and some other factors.


Personal taste and preference determines the cut of the diamond.  When jewelers judge the quality of a cut diamond, they often rate "Cut" as the most important of the "4-Cs."  The shape is not key, but how well the cutters executed the shape.  Since the brilliance and fire of a diamond depends on the angle of the facets in relation to each other.  A poorly cut diamond with facets cut only a few degrees from optimal will result in a stone that lacks the gem quality.  If a diamond is cut for fire, rather than a balance between brilliance and fire
it looks more like a cubic zerconi which gives out more fire than a real diamond.

Cutters can compromise and accept lesser in order to avoid inclusions or to preserve the carat rating.  Since the per-caret price of diamond is much higher when the stone is over one caret.  Many one-caret diamonds are the result of compromising "Cut" for "Caret". Jewelers may advise to buy a 0.99 carat diamond  for a better price or buy a 1,10 carat diamond for its better cut.  A 1.00 carat diamond is usually poorly cut.

Some of the stone cuts are:
Round
Radiant
Pear
Marquise
Emerald
Oval
Heart
Princess

These choices remain with the customer and vary with each individual.