In short: Work out the volume of the piece in cubic centimetres and multiply it by the metal's density: about 10.3 g/cm³ for sterling silver, 10.5 for fine silver and 11.3 for 9ct gold. Add a waste margin, often 10–25%, then multiply by the current metal price per gram to get your raw material cost.
Precious metal is expensive and sold by weight, so "how much do I need?" is a question with real money attached. Order short and you stall mid-project waiting on stock; order long and you've tied up cash in metal you don't need yet. A little arithmetic before you buy puts you in control.
The basic method: volume × density
Every metal has a known density (sterling silver ≈ 10.3 g/cm³, 9ct gold ≈ 11.3, fine silver ≈ 10.5). Work out the volume of your piece in cubic centimetres, multiply by the density, and you have the weight. For sheet: length × width × thickness (all in cm) = volume. For wire: it's a long cylinder — π × radius² × length. Round generously and add a margin for waste, solder and finishing losses. Worked example: a sheet pendant 30 × 30 mm at 1 mm thick is 3 × 3 × 0.1 cm = 0.9 cm³, which in sterling is about 9.3 g before any piercing waste.
Measure accurately first
Garbage in, garbage out — your estimate is only as good as your measurements. A micrometer reads sheet and wire thickness to 0.01 mm, dividers and calipers step off lengths, and a wire/sheet gauge confirms stock thickness at a glance. These live in Measuring & Marking. A 0.1 mm error on thickness scales straight through to the weight.
The easy shortcut: weigh a model
If you've carved a wax or made a model, you don't need the maths at all. Weigh the wax, then multiply by the metal's casting factor (silver ≈ 10.5× the weight of the wax; 9ct gold ≈ 11.5×). It's the quickest, most reliable estimate for cast pieces — far easier than calculating an organic shape's volume by hand.
From weight to cost
Multiply the finished weight (plus your waste margin — often 10–25%) by the current metal price per gram, and you have your raw material cost. Bullion prices move daily, so check a live spot price the day you buy rather than last month's figure — on a heavy piece the difference is real money. That's only the start of pricing a finished piece, of course — time, skill, overheads and margin all sit on top. Our guide to pricing trade vs retail builds the full picture, and measuring at the bench and the wire gauge guide keep your inputs accurate.
Find measuring tools in Measuring & Marking and Mandrels & Sizing.
Frequently asked
How do I work out the weight of a sterling silver sheet pendant?
Multiply length × width × thickness in centimetres to get the volume, then multiply by the density of sterling. A pendant 30 × 30 mm at 1 mm thick is 3 × 3 × 0.1 cm = 0.9 cm³, which in sterling is about 9.3 g before any piercing waste.
How do I calculate the weight of jewellery wire?
Treat the wire as a long cylinder: π × radius² × length gives its volume, and multiplying the volume by the metal's density gives the weight. Round generously and add a margin for waste, solder and finishing losses before you order.
How do I estimate how much metal a casting needs from its wax model?
Weigh the wax and multiply by the metal's casting factor: about 10.5 times the wax weight for silver and about 11.5 times for 9ct gold. It is the quickest, most reliable estimate for cast pieces, and far easier than calculating an organic shape's volume by hand.
How accurately should I measure sheet thickness when estimating metal weight?
As accurately as you can, ideally with a micrometer, which reads sheet and wire thickness to 0.01 mm. A 0.1 mm error on thickness scales straight through to the weight. Step off lengths with dividers and calipers, and confirm stock thickness at a glance with a wire or sheet gauge.