The WorkbenchPricing
Wax-to-Metal Casting Calculator
Weigh the wax, pick the metal — the grams to weigh into the crucible, button and sprues included, split into fine metal and alloy.
The wax
Weigh the whole tree if you can — model, sprues and feeders together. That is the number the metal has to fill.
Start from a typical flask
The 15% is a placeholder for a tree nobody weighed. Sprue weight depends on how you tree, so weigh one finished tree and switch to the tab above — it is the single biggest source of error in this sum.
Wax is about 1 g/cm³, so the multiplier is simply the metal's density.
Button & cycle lossoptional
Both are your bench's numbers. The defaults are cautious, not authoritative.
Calibrate on one real castoptional
Your wax and your machine, instead of a table. This is free and it beats every figure above.
Densities are published figures for cast alloys and vary a little by recipe. The button and the cycle loss are your numbers — the defaults are deliberately cautious. Calibrate on one real cast and none of that matters.
Work faster
A bench book of measured factors, a mixed tree, and the charge sheet as CSV come with Tools Pro. We're checking whether yours is active — they appear here by themselves if it is.
Sellers also ask
How do I calculate metal weight from wax weight?
Weigh the wax, then multiply by the metal's density divided by the wax's. Jewellery injection wax sits close to 1 g/cm³, so the multiplier lands near the density figure itself — about 19.3 for fine gold, 17.7 for 22K, 15.5 for 18K yellow, 10.4 for sterling. Waxes differ between suppliers, so cast one known model and weigh the metal: that ratio is your bench's real factor, and the calibration step here keeps it.
How much extra metal do I need for the sprues and the button?
Weigh the whole tree in wax — model, sprues and feeders — not just the piece. The button on top is a reservoir that feeds shrinkage as the metal freezes; too small and the piece comes out porous near the sprue. Its size depends on your flask, machine and tree weight, so cut off three of your own buttons, weigh them, and use that number instead of a table's. None of it is lost — it returns as clean melt stock, and this calculator counts it as a return rather than a loss.
I need 60 grams of 22K in the flask — how much fine gold and how much alloy?
Multiply by the fineness. 22K is 916, so a 60 g charge is 54.96 g fine gold and 5.04 g alloy; 18K is 750, which makes it 45 g and 15 g; 14K is 585 and sterling is 925, fine silver with copper. Weigh both parts on the same scale before they go in. Common bench practice is to hold reclaimed sprue and button metal to about half the charge and make the rest up with fresh metal.
Why did my casting come out half-filled?
Almost always too little metal in the crucible, or a button too small to feed the shrinkage. Metal contracts as it freezes and the button is the reservoir that makes up the difference — undersize it and the last thing to fill starves. Check the tree weight you multiplied from as well: weighing the model and forgetting the sprues under-charges the flask by roughly the sprue share every single time.
Is this casting calculator free, and what does Tools Pro add?
The whole calculation is free with no daily cap — the charge, the button, the split into fine metal and alloy, what returns as sprue and button, and calibrating on your own cast so the factor is your bench's rather than a table's. Tools Pro adds a bench book of measured factors for shops running more than one wax or flask, a mixed tree of several designs on one flask, and the charge sheet as a CSV file for the issue register.