Table width is quoted in percent (width divided by the average stone diameter). Table size is less critical to the beauty of a diamond than variations in than crown and especially pavilion angle. AGS and GIA’s new systems each have top grades that include 61% table sizes (AGS will go down to 47%).
Yields from most rough diamonds are improved by polishing larger table sizes than we might prefer. Small variances in crown and pavilion angles cause less problems if table sizes are in the range of 55% to 58%.
Larger table diamonds have a better "spread" and can be brighter, i.e. they return more light, but are often less firey than diamonds with smaller tables. They often have less scintillation. Larger table sizes are considered to be an advantage in smaller diamonds below .10ct.
The ability of a diamond to break light into rainbow colors, called fire or dispersion, is enhanced by light entering or leaving a diamond at an acute angle; a larger table size means a smaller crown facet area, the part that creates most dispersion. The same principle applies to cut crystal wine glasses and chandeliers. Visualize the Pink Floyd "Dark Side of the Moon" CD cover. Technically, dispersion is maximized as light approaches the critical angle between the diamond to air interface. The resultant burst of color emerges close to parallel to the surface of the diamond. So if you look from the front of a diamond you are more likely to observe fire from a crown facet which is greater in size when the table is smaller.
Scintillation is the other casualty of a large table; your line of sight is "bent" more by crown facets, so you look more deeply into the diamond and there may appear to more flashing sparkles you observe as you roll a diamond with a small table. Old cut diamonds often have very small tables (and steeper crown angles) and sometimes you can see the culet in the crown facets 4, or even 8 times, from a face up view.
You can see on the images here that the smaller table diamonds appear to have more facets than the larger table images. If a diamond had no crown facets it would appear boring.
Table sizes over 60% are more affordable and because there is less crown height, they have a larger spread or diameter. You get a bigger looking rock for less cash. We suggest an upper limit of 63%. You will see that Ideal-Scope images of larger table diamonds often look a little paler just inside the table; but what appears to be 50% pink intensity will actually return 75% or more light.
As table sizes get larger, beware of the fish-eye effect.