What the Numbers Can and Cannot Tell You

The table is the large, flat facet at the very top of a faceted diamond. The total depth runs from the table surface down to the lowest point or culet. On many grading reports, table and depth are listed as percentages so stones of different physical sizes can be compared proportionally.

For a round diamond, percentage calculations use average girdle diameter. For fancy shapes, reports commonly compare measurements with the width, but the way a laboratory presents data can vary by report type. Read the labels and diagram rather than assuming every report uses the same convention.

Table percentage is generally the table width divided by the diamond's overall width, multiplied by 100. A larger percentage means the top facet occupies more of the face-up surface. A smaller table leaves more room for the crown facets surrounding it.

A large table is not automatically bright, and a small table is not automatically fiery. The result depends on the crown height, crown angle, pavilion structure, star facets, lower-half facets, and how all of those parts return and disperse light.

Total depth percentage is generally the stone's depth divided by its width, multiplied by 100. A deeper diamond may carry more of its weight vertically, which can reduce face-up spread. A shallow stone may look wider for its weight but can lose light through the pavilion if the angles do not work together.

This does not mean that the lowest depth percentage is best. The goal is coordinated geometry. Two diamonds can share the same total depth yet distribute that depth differently between the crown, girdle, and pavilion. Their light behavior and apparent size may therefore be very different.

The crown receives and disperses light, while the pavilion directs much of the light back toward the viewer. If one is too steep or shallow relative to the other, a diamond may leak light or show an undesirable contrast pattern even when the table and total depth fall within a commonly recommended range.

This interaction is why shoppers should resist "single-number shopping." Filters can be useful for narrowing a large list, but they cannot replace images, videos, grading information, and comparison under consistent lighting.

Modern round brilliant diamonds often receive a laboratory cut grade that considers multiple proportion and finish factors. Many fancy shapes do not receive a universal overall cut grade. Their table and depth values are still informative, but shape-specific features such as bow-tie contrast, corner shape, length-to-width ratio, facet distribution, and symmetry take on greater importance.

A proportion range that produces attractive results in one shape cannot simply be transferred to another. Even within the same shape, different facet arrangements can use similar table and depth percentages to create different visual patterns.

Carat measures weight, not diameter. Depth percentage helps explain why two diamonds of equal weight may face up at different sizes. A deeper stone can hide weight below the girdle, while a shallower stone may spread more. However, spread should never be considered without light performance and edge durability.

Compare actual millimeter dimensions alongside the proportions. If a diamond looks large but has a weak center or fragile girdle, the apparent size is not a worthwhile trade. A balanced diamond uses its weight in a way that supports beauty and wearability.

• Use table and depth percentages to understand geometry, not to declare a winner.
• Read crown, pavilion, girdle, culet, polish, and symmetry information when available.
• Compare exact millimeter measurements for face-up size.
• Review videos that show the diamond moving in neutral lighting.
• Examine fancy shapes for outline balance and persistent dark areas.
• Choose the stone before finalizing a custom setting.

Neptunes Jewelry offers a designer-led process in which diamond selection, setting, and metal can be considered together. A report provides essential documentation, but the final choice should also reflect how the actual diamond looks and how its proportions fit the intended setting.