How do you determine a round brilliant diamond's table size?

• A. Measure the table facet in four directions and average the measurements.
• B. Estimate table size by visual inspection.
• C. Measure the table in two directions and double the result.
• D. Use girdle diameter to approximate.

Answer: (A)

Determining a round brilliant diamond’s table size comes down to measuring the actual width of the table facet across multiple directions and using that to gauge how large the table appears relative to the stone as a whole. The table is the wide, flat top facet, and its width is most accurately captured by taking measurements across the table in four perpendicular directions with calipers, then averaging those four readings. This average table diameter accounts for any slight irregularities in the stone’s shape or table surface, giving a stable, representative value rather than a single, potentially biased measurement. Once you have the average table diameter, you express the size as a percentage of the overall diameter (girdle-to-girdle) by dividing the table diameter by the overall diameter and multiplying by 100. Visual estimation or relying on only two directions introduces error, and using the girdle diameter alone would not reflect the true table width.