Wax tree on the scale, burnout in the morning
Weigh the tree, pick your metal, and get the cast weight, the grain to weigh out, and what the metal in the piece actually costs — plus a quick answer when a customer asks for the silver design in 14k. Everything stays in your browser.
The flask
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The numbers here are yours to check. This page does arithmetic on what you type — it cannot see your recipe, your equipment or your batch.
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In MadeKeeper, the grain you weigh out and the button you weigh back in both live in your inventory, so each casting lands in the ledger carrying only the metal it actually consumed — gross melt minus the returned button — at your real per-gram price. See for metalsmiths or poke around the live demo. $19/mo for the whole back office, kept for as long as you stay. The shop stays free for cost a piece and one fair — no product cap. The tax packet, Etsy and Square, and more fairs are the $19.
Free calculator for jewelers
The formula itself is old bench math — wax weight times specific gravity — but nearly every number inside it gets argued over. Here's where our defaults come from, and which ones you should change to match your own bench.
How do I convert wax weight to metal weight?
The bench formula is: metal grams = wax grams divided by the wax's specific gravity, times the metal's specific gravity. The shortcut you probably learned — just multiply wax weight by the metal's SG — quietly assumes your wax has an SG of 1.0, which is close for most injection waxes, but carving and injection waxes actually run about 0.92 to 0.96, so wax SG is a setting here, not a constant — the default is 0.92, which is what Ferris publishes for all six File-A-Wax carving formulas; their injection waxes run 0.95 to 0.96. An 8 g tree cast in sterling (SG 10.36) works out to about 90.1 g of metal.
How much extra should I melt for the sprue and button?
This is the most argued number in casting, and the honest answer is that every caster holds their own — somewhere between +20% and +50% over the cast weight, depending on flask size, how big a button they like, and how much they trust their scrap. We default to +50 because running short mid-pour ruins the flask, and the buffer isn't really spent — the button cools, gets clipped, and goes back in your grain jar. On the 8 g example, 90.1 g of cast sterling means weighing out about 135.1 g of grain. That's exactly why it's a setting and not a constant: your allowance is a habit you've earned, not a law.
A customer wants my silver piece in 14k — how do I quote the weight?
Same math, metal to metal: take the model's weight, multiply by the target metal's SG, divide by the current metal's. A 6 g sterling model comes out around 7.57 g in 14k yellow — that's 6 × 13.07 ÷ 10.36. One catch: "14k" isn't a single number, because alloys run roughly 12.9 to 13.6 depending on the mix, so the 13.07 default is a convention you can override with your supplier's figure in Metal SG above — and on a heavy piece that spread is a real difference in the quote.
Why does the cost only price the cast weight, not the whole melt?
Because the button isn't consumed. It comes out of the flask, gets cleaned up, and returns to stock for the next pour — what actually left your inventory is the cast weight. So the piece carries 90.1 g of sterling at your grain price, say $1.20 a gram, for $108.12 of metal in the casting, even though you weighed out 135.1 g. Pricing the full melt would charge the same buffer against every piece you ever make.