Casting Grain Calculator

Lost-wax casting replaces a wax model with metal of the identical shape, so the core trick is a straightforward density ratio: since the wax model's weight is known and standard injection wax has a fixed density of about 0.97 g/cm³, multiplying the wax weight by (metal density ÷ 0.97) gives the weight of metal that will fill that exact same volume once cast. This calculator applies that ratio using density values for sterling silver (10.49 g/cm³), 14k gold (13.07), and brass (8.5) — so casting the same wax pattern in 14k gold takes roughly 25% more metal by weight than sterling silver, purely because gold alloy is denser, not because the piece is bigger. On top of the piece's own metal weight, the calculator adds a sprue-and-button allowance (default 50%, adjustable 20-100%) to account for the wax sprues, gates, and casting button that form the tree connecting your model to the crucible during the burnout and casting process — metal that fills the tree but gets cut away afterward.

More complex trees with multiple pieces or intricate sprue networks need a higher percentage; a single simple piece on a short sprue can often get by with less. Results are also converted to troy ounces and pennyweight, the units precious-metal suppliers price grain in. Because the 0.97 g/cm³ wax density is a standard average, casting wax blends and injection temperatures vary slightly between suppliers — weigh your actual wax model on a jewelry scale rather than estimating it, since that's the input this whole calculation hinges on.