What are the ideal proportions for a round diamond?

A round brilliant looks best with a table around 54–57%, total depth of 59–62.5%, a 34–35° crown angle and a 40.6–41° pavilion angle.

Why do proportions matter more than carat?

Well-proportioned diamonds reflect more light, appearing brighter and often larger than poorly cut stones of the same weight. For visual impact, good proportions outweigh a slightly higher carat.

How do I check a diamond's proportions?

Read the proportion diagram on the GIA report, or use a tool like the Holloway Cut Advisor (HCA) to score a round diamond's light performance from its measurements.

What are Diamond Proportions?

Q: What are diamond proportions?

Proportions are the relationships between a diamond's table, depth, crown and pavilion angles. They determine how light reflects within the stone and back to your eye, driving brilliance and fire.

Quick Answer

What are ideal diamond proportions?

Proportions are the relationships between a diamond's facets, table, depth and angles, and they determine how light bounces back to your eye. For a round brilliant, a table around 54-57%, a total depth of 59-62.5% and a 34-35 degree crown angle deliver ideal brilliance. For sparkle, good proportions matter more than a high clarity or colour grade.

Reviewed by Winnie GIA-certified Gemologist Updated Aug 19, 2026

DIAMOND PROPORTION – UNDERSTAND BRILLIANT, FIRE AND SCITILLATION

WHAT IS DIAMOND PROPORTION ?

Excellent cut diamond will show three different qualities: brightness, fire and scintillation.

Excellent cut diamond will show three different qualities: brightness, fire and scintillation.
Brilliant: When light shines on the diamond surface by the drill will enter the table, while the bottom of the white diamond will reflect back, this internal reflection external white light is the brightness of the diamond.
Fire: a diamond shining in the light, some light will be split become Diamond colorful spectrum of colors, the process of creating a diamond color of fire.
scintillation: flash refers to the viewer to move the diamonds so that you can see its brilliance, black and white contrast due to internal reflection of light caused.