Metal Weight Calculator.

Carit's metal weight calculator converts a wax model weight to casting weight in any of 20+ jewellery alloys - 9k, 10k, 14k, 18k, 22k and 24k gold in yellow, white and rose, plus platinum, palladium, sterling silver, fine silver, brass, bronze, copper, titanium and more. This page explains how the calculator works, the industry-standard specific-gravity values it uses, and when to reach for each variant in the app.

How the Carit metal weight calculator works

The metal weight module in Carit is actually five separate calculators sharing one engine. Picking the right one saves you a manual conversion and a second check.

1. Wax to metal

Weigh your wax model on a jewellery scale, type the weight into Carit, pick the target alloy from a scrollable list of 20+ metals. The app multiplies wax weight by the published specific gravity of the chosen alloy, applies a small casting buffer (1-2%) to account for shrinkage and finishing loss, and shows the estimated casting weight in grams, pennyweight and troy ounces.

2. Ring weight

Given inner diameter, outer diameter and width, the ring weight calculator derives the volume of a plain band and multiplies by the selected alloy's density. Useful before you cut a shank - you know exactly how much metal to grain.

3. Wire, sheet and tube weight

Each uses the appropriate volume formula (π·r²·L for wire, L·W·T for sheet, tube has inner and outer radii). Weight falls out of the volume × specific gravity calculation. Works in millimetres, inches or whatever unit you've set the app to.

4. Integrated live metal prices

Every metal weight result in Carit is optionally multiplied by the current spot price of the alloy's precious-metal content, pulled live and cached. So a 26 g ring in 14k yellow gold shows not just "26 g" but "$840 of raw material at today's spot". Live pricing is a Carit Pro feature.

The formula (it's just specific gravity)

Casting weight in any given metal is simply the wax weight multiplied by the specific gravity of that metal, divided by the specific gravity of the wax. For most standard jewellery wax (blue inlay, green milling, red pattern), the specific gravity is approximately 0.98 - so close to 1 that most benches simply treat it as 1.0 and use the metal's specific gravity as a "wax-to-metal factor" directly.

That gives you the working formula every goldsmith memorises:

A 1 g wax model, cast in 18k yellow gold (specific gravity 15.58), gives a casting weight of approximately 15.58 g. Cast the same wax in sterling silver (SG 10.36), you get 10.36 g. Cast it in platinum 950 (SG 20.76), you get 20.76 g.

Real-world casting adds about 2% to 5% on top of the theoretical weight to account for sprue, shrinkage and finishing loss. Carit's factors include a conservative 1.5% buffer by default - enough to quote a casting accurately without running short when the metal lands on the bench.

Full specific gravity table for jewellery metals

These are the values used in every calculation on this page. They're cross-checked against Stuller, Rio Grande, and Cooksongold published figures, and they'll match almost any professional bench reference to within the second decimal.

Worked examples

Example 1 - A 2 g wax ring in 14k rose gold

14k rose gold has a specific gravity of 13.10. The calculation is:

Example 2 - A 3.4 g wax pendant in platinum

Platinum 950 has a specific gravity of 20.76. Platinum always surprises first-time platinum casters:

Example 3 - A 1.1 g wax band in 22k yellow gold

22k gold, beloved of Indian and Middle Eastern jewellery, has a specific gravity of 17.80:

Why wax weights matter

Casting is the single biggest cost in most jewellery pieces. Ten grams of 18k yellow gold is roughly $280 in raw material. Getting the wax-to-metal calculation wrong by 10% isn't a rounding error - it's $28 per casting, on every casting, forever. Over a year of production that compounds into real money.

The goldsmith who keeps a specific-gravity table in their head and runs this calculation from the first wax has two advantages: (1) they never run short of casting grain, and (2) they quote consistently, because their quotes are grounded in the actual metal weight they'll pay for.

How to weigh a wax accurately

A standard jewellery scale with 0.01 g resolution is enough. Sit the wax directly on the pan - no wax containers, no tissue paper, nothing that adds weight. If the piece is asymmetric, weigh it in two orientations and average.

If you're casting from a 3D print rather than a hand-carved wax, the software that generated the print (MatrixGold, RhinoGold, Fusion 360, Blender) usually has a volume readout. Multiply the volume in cubic centimetres by the specific gravity of your resin (check the manufacturer data sheet - it's typically 1.05 to 1.15 for castable resins) to get the theoretical "wax-equivalent" weight. From there the calculator above handles the rest.

Metal weight for specific shapes

If you don't have a wax yet but you know the dimensions of the piece you're planning, you can estimate weight from volume. For standard shapes the formulas are well known.

Ring weight (plain band)

Volume = π × ((outer radius)² − (inner radius)²) × width. Multiply by specific gravity for weight.

Wire weight

Volume = π × (radius)² × length. Cut a 1 m length of 1.5 mm 18k yellow gold wire: volume = π × 0.75² × 1000 = 1,767.1 mm³ = 1.767 cm³. Weight = 1.767 × 15.58 = 27.52 g.

Sheet weight

Volume = length × width × thickness. A 50 × 50 × 1 mm sterling silver sheet: 2,500 mm³ = 2.5 cm³ × 10.36 = 25.9 g.

Tube weight

Volume = π × (outer radius² − inner radius²) × length.

The Carit app has dedicated calculators for each of the above - ring weight, wire weight, sheet weight, tube weight - so you don't need to do the geometry by hand.

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