The Quality of the Diamond Cut 

What should you look for in depth percentage (height) and table percentage? Probably the most crucial dimension of the stone is the height which should be between 60-62%. Table percentage should be 53-63% ... 

The recommended cut height for a Round Brilliant is 59.3% that of the diameter of the diamond, which breaks down to about 43% for the pavilion, and 16% for the height of the crown. This 59% is probably the most crucial dimension of the stone. When buying a diamond, don't forget to add 1-2% for a decent girdle, so you are really looking for 60-62% for this type of cut.

You will see diamonds that are too shallow (the height is significantly smaller than 59%) or too chunky (significantly over 59%). Don't buy stones which deviate too much from this value.

In practical terms you want to find a diamond at approximately 60% depth and 60% in table percentage as a good rule of thumb.

Probably the most noticeable proportion on a Brilliant Cut diamond is the size of the table.