As with the crown angle, if the pavilion angle is too large, it will not emit notable sparkle. If it is too shallow, the diamond could appear glassy. When cut for brilliance, the pavilion will reflect the most sparkle to your eye through the top of the diamond.

It is key for a diamond's pavilion to not be too deep or shallow. An overly deep pavilion will bring a darkened effect to the stone, as it is not able to reflect enough light back up to the observer's eye through the crown. A shallow pavilion will bring a 'fish-eye' effect if viewed from the table. This is because the girdle will be reflected in the middle of the diamond, appearing dull and lacking in scintillation.

The optimum pavilion angle is between 42.5% and 43.5%. This percentage will be labeled on the diamond's grading report. Both the GIA and AGSL list the pavilion depth and angle, and the diamond's depth as a whole. All of these measurements are considered when the diamond's cut grade is being assessed.

The bulk of a diamond's weight is typically held in its pavilion. This means it is often considered the most valuable part of the diamond, and yet its angles are more important than its size. A large pavilion that is too shallow or deep will not help create the brilliance that shoppers are looking for in their diamond.