“How much will it weigh?” is one of the hardest questions in custom jewellery — and the customer always asks it. Precious metals are among the most expensive and dense materials a designer works with, so small miscalculations move the price significantly. The professional answer is not one method but four, each trading speed for accuracy, and the first job is setting expectations: it is nearly impossible to build a design to hit an exact weight or budget on the fly, and the honest studio assures the customer they pay for the actual metal used, not the estimate.
Method one: compare to a similar piece
The most common quick estimate: find a finished piece with dimensions reasonably close to the paper design — in the desired metal — and weigh it. Fast, but the least accurate: by-eye estimates are commonly off by two to three times, occasionally by an order of magnitude. It is a conversation tool, never a formal quote.
Method two: the kneadable-eraser mock-up
With a little more time, the designer shapes a rough mock-up of the design in a kneadable eraser, weighs it, and multiplies by a conversion factor for the target metal. The training table runs from fine gold at 9.7 and fine platinum at 10.7 down to sterling silver at 5.2, with the karat golds and platinum alloys between. Better than guessing — but still potentially 30 to 90 percent off, depending entirely on how faithful the mock-up is. It can be done while the customer waits.
Method three: weigh the wax
When a design is finalized and headed for lost-wax casting (see the lost-wax casting process), the wax model itself becomes the estimator: weigh the wax, multiply by the metal's factor — fine gold 19.32, 22K gold 18.22, 18K gold 15.50, fine platinum 21.45, fine silver 10.49 — and the result is typically within about 15 percent. The catch: the design must be final before the wax exists.
Method four: CAD modelling
The most accurate route is a CAD model of the piece, whose built-in weight-estimation tools land typically within 5 to 10 percent — with the bonus that the design can still change after the estimate, responding to the customer's reaction to the number.
Why the “market price” is not the price
Precious metals are publicly traded commodities, and their market prices are published online — but that commodity price is what banks and refineries pay for bullion. By the time metal reaches a jeweller it has passed through additional processes and costs, so consumer metal prices sit above the chart. Unit conversions matter too: one troy ounce is 31.1 grams, one leung is 37.8 grams, and a price quoted per kilo must be brought down to the gram before it means anything for a ring. Weight is only half the story of a quote — the other half is in how stone value is decided, and the estimation skills above are taught across the gemmology and design curriculum, from gem-weight estimation for designers to the full certificate programmes.