Diamond Table, Depth & Culet Explained
Three proportion terms that together determine how well a diamond returns light — what the percentages mean and what to look for.
Table, depth and culet are the three proportion measurements that, together, do more to determine a diamond's brilliance than almost anything else on a certificate.
Table percentage
The table is the large, flat facet on the very top of the diamond. Table percentage is the table's width divided by the stone's overall width — for a round brilliant, an excellent-grade table typically falls in the 54–57% range, though ideal ranges genuinely differ by shape. Too large a table lets light escape before it's properly dispersed through the stone's other facets; too small reduces the stone's overall brightness.
Depth percentage
Depth percentage is the diamond's total height (culet to table) divided by its width. This is the single number most responsible for whether a stone shows windowing or extinction (see our windowing and extinction guide) — a round brilliant's excellent-grade depth typically falls around 59–62.6%; too shallow and light leaks out the bottom (windowing), too deep and light gets trapped without returning (extinction), and it also directly affects spread — deeper stones sit smaller face-up for the same carat weight.
Culet
The culet is a tiny facet, if present at all, at the very bottom point of the diamond, added historically to reduce chipping risk at that vulnerable point. Modern cutting can achieve none-to-small culets safely; culet size grades range from None through Small, Medium, Slightly Large, Large, up to Very Large. None-to-Small is what most current cut-grading standards look for; anything Medium or larger shows as a visible dot at the centre of the table when viewed face-up and is considered a genuine cut flaw at that size.
Reading these together
No single one of these three numbers tells the whole story — a diamond can have a good table but a poor depth, or vice versa. The three together are what a lab's overall cut grade (Excellent, Very Good, etc.) is actually summarising, which is why checking the cut grade alongside these individual numbers — rather than either alone — gives the clearest picture of how well a specific stone will perform.
Related reading
Source: ideal table/depth ranges by shape and culet grading per current trade-jeweller education content (Brilliance, PriceScope, Beyond4Cs, Willyou).
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