Diamond Weight Calculator

Because diamonds are cut into various geometries, our calculator uses distinct formulas for round stones versus fancy shapes (such as oval, princess, emerald, or cushion cuts). For standard round brilliant diamonds, the calculation relies primarily on the average diameter squared multiplied by the depth and an empirical constant of 0.0061. For fancy shapes, the equation factors in length, width, depth, a geometric adjustment factor specific to the diamond's outline, and multipliers for girdle thickness and overall weight correction.

Imagine you have a round brilliant diamond with a measured diameter of 6.5 millimeters and a depth of 4.0 millimeters. Assuming a standard girdle thickness factor that equals 1, the calculation for a round shape is performed as follows: weight equals diameter squared (6.5 squared = 42.25) multiplied by depth (4.0), which yields 169. Multiply 169 by the empirical constant 0.0061 to arrive at an estimated weight of approximately 1.03 carats.

To achieve the most accurate carat estimations, always use a calibrated digital caliper capable of measuring down to hundredths of a millimeter. When measuring depth, measure from the table surface down to the culet tip carefully, avoiding any prong obstructions if the diamond is already set in jewelry. Keep in mind that calculated carat weights are approximations and can vary slightly based on actual pavilion angle depths and girdle variations.