A girdle thickness of greater than “Medium” will require you to add a percentage to the weight estimation formulas for greater accuracy. If a girdle thickness adjustment (GTA) has not been added into the formula, assume the girdle to have a Medium average thickness. If it is thicker, a weight percentage must be added for the stone in question. Typically fancy shapes will have thick to extremely thick girdles due to the cutter’s attempt to blend the shape of the stone. These weights will always have to be adjusted for this characteristic. Rounds and fancy shapes commonly have varied girdle thicknesses, so an average value can be used.