Approximately how much does a full-cut round brilliant diamond with a 6.50mm girdle diameter weigh?

A full-cut round brilliant diamond with a girdle diameter of 6.50mm typically weighs approximately 1.00 carat. This estimation is based on the standard measurements and weight-to-diameter ratios established in gemology, particularly for round brilliant cuts.

Diamonds are commonly measured in carats, which is a unit of weight equivalent to 200 milligrams. The weight of diamonds can vary slightly based on factors such as cut quality, proportions, and overall shape, but the 6.50mm size is generally associated with a weight around 1.00 carat. This size is often used as a reference point in both jewelry retail and appraisals, making it a core concept in understanding diamonds.

Thus, when estimating the weight of diamonds based on their diameter, the 1.00 carat designation for a 6.50mm stone aligns with the standards used in the industry for round brilliant diamonds.