The table is the top facet of a diamond, expressed as a percentage of the diamond's average girdle diameter. This is the largest facet of a stone, and the one that is presented first. If the percentage is too low or too high, there will be more light leakage and the diamond will sparkle less.
Because the table is the diamond's main entry and exit point for light, the size of the table determines the overall "look" of the diamond. The bigger the table, the greater the sparkle, because the stone returns more light, but at the cost of less fire. Conversely, the smaller the table the greater the fire, at the cost of having less sparkle. It is important to note that a diamond should not be chosen solely according to table %, as depth %, symmetry, girdle, and clarity grade need to be factored into the equation.
Table width is quoted as a percentage on an official lab-issued diamond certificate. Table sizes over 60% are typically more affordable because they have less crown height—expert advise consumers not to exceed 64% on table size. It is important to note that different diamond shapes, such as round, princess, emerald, etc. have different ideal table sizes.