Depth percentage is the total height of a stone — from table to culet — expressed as a percentage of its width at the girdle. A round brilliant with a 61% depth and a 6.5mm diameter has a total height of approximately 3.96mm. This single number sits at the intersection of two of a buyer's most important concerns: optical performance and apparent size.
Too shallow — below roughly 58% for a round brilliant — and the pavilion angle drops below the critical angle for total internal reflection. Light stops bouncing between pavilion facets and leaks straight through the bottom. The stone goes dark in the center, an effect sometimes called a "fish-eye" or "nail-head." Too deep — above roughly 63% — and the stone buries mass in its pavilion. It is heavier than it looks. You pay for carat weight that never shows up on a hand.
| Cut | Ideal depth % | Acceptable range | Notes |
|---|---|---|---|
| Round Brilliant | 59–62.5% | 58–64% | GIA Excellent requires 57.5–64% |
| Princess | 64–75% | 62–80% | Naturally deeper than round; accept up to 75% |
| Oval | 58–62% | 56–68% | Depth also affects bow-tie severity |
| Pear | 58–62% | 55–68% | Shallower than 58% risks bow-tie extinction |
| Marquise | 58–62% | 56–66% | Deep marquise narrows apparent outline width |
| Cushion | 61–67% | 58–72% | Modified cushions run deeper; check dimensions |
| Emerald | 60–67% | 58–72% | Step cuts can accommodate deeper proportions |
| Asscher | 60–75% | 58–78% | Deep pavilion intentional for optical X effect |
| Radiant | 61–67% | 58–72% | Similar to cushion; check face-up dimensions |
| Heart | 56–62% | 54–66% | Deep hearts narrow apparent width considerably |
When evaluating a fancy shape, always check the millimeter dimensions alongside depth percentage. A 1-carat oval at 68% depth may have the same face-up area as a 0.85-carat oval at 62% depth — you are paying for 15% more weight that sits hidden beneath the setting. This is one of the most common value traps in fancy shape purchasing, and it is entirely visible on the grading report if you know to look for it.
Your cert lists the depth percentage. Drop it into the Cert Checker to see whether it falls inside the ideal range for your cut.
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