Since diamond is a valuable commodity, the dealer must approach its valuation with as much accuracy as possible. Alarge part of this accuracy lies in determining an estimated weight to the best of his (or her) ability. If all diamonds — rounds and fancy shapes — were cut in the same exact proportions, we could use the hole gauges, plastic templates, or diameter measurements alone, to determine fairly accurate weight estimates. Common sense tells us that a deep 6.5 mm diameter stone is going to weigh more than a shallow 6.5 mm diameter stone. This is why weight formulas are of utmost importance.