Crown Height Percentage is defined as the distance from the girdle plane to the table, expressed as a percentage of which measurement?

• A. average girdle diameter
• B. table diameter
• C. crown height
• D. pavilion depth

Answer: (A)

Crown height percentage compares how tall the crown is to the stone’s overall width, giving a size-normalized measure. The crown height is the distance from the girdle plane up to the table, and it’s expressed as a percentage of the average girdle diameter—the horizontal dimension that best represents the stone’s overall width. This normalization lets you compare crown heights across stones of different sizes. The standard relationship is CHP = (crown height ÷ average girdle diameter) × 100.

Using the table diameter wouldn’t reflect the overall size, since it’s a top dimension, not the stone’s width. Using crown height as the base would remove any size context, and pavilion depth relates to the bottom portion, not the crown.