What is table percentage in a diamond?
By Jared James · Last updated 21 May 2026
Definition
Table percentage is the measurement of a diamond's table facet width expressed as a percentage of its average girdle diameter. So if a round brilliant measures 6.5 mm across the girdle and the table spans 3.7 mm, the table percentage is about 57 percent. It is one of the key proportions grading labs record, because the table size influences how light enters the stone and whether the cut produces a strong balance of brightness and fire. For round brilliant diamonds, a table percentage between about 54 and 60 percent is generally considered the ideal range for maximum light performance.
Frequently asked questions
- What is an ideal table percentage for a round brilliant diamond?
- Most gemologists and grading labs consider 54 to 60 percent the sweet spot for round brilliants. Within that range the stone tends to return strong white light while still generating coloured fire at the crown edges. AGS and GIA both factor table percentage into their overall cut grades.
- Does table percentage matter as much for fancy cuts?
- Fancy shapes like ovals, cushions and emerald cuts have their own preferred proportion ranges, and the ideal table percentages differ between shapes. The principles are the same but the numbers change, and for step cuts like the emerald, table size affects the broad hall-of-mirrors effect rather than the fire of a brilliant.
- How is table percentage calculated?
- It is the table width divided by the average girdle diameter, expressed as a percentage. Grading reports from labs like GIA list this figure alongside depth percentage, crown angle and other proportions, so you can check it directly on a diamond's certificate.
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