How to calculate gold weight from a 3D model
Multiply the model's volume by the density of the alloy. Measure the solid volume of the ring in cubic centimetres, then multiply by the alloy density in grams per cubic centimetre. A 14K yellow gold band holding 0.21 cubic centimetres of metal weighs about 2.7 grams, because 14K yellow gold is 13.07 grams per cubic centimetre.
3D Jewelry Designer2 min read
What you need before you start
Two numbers, and only two. The solid volume of the ring in cubic centimetres, and the density of the alloy you will cast it in. Everything else, including finger size, band profile and stone count, matters only because it changes one of those two numbers.
The formula
grams = volume (cm³) × density (g/cm³)CAD software usually reports volume in cubic millimetres, and there are 1,000 cubic millimetres in a cubic centimetre. So from a millimetre measurement:
grams = volume (mm³) ÷ 1000 × density (g/cm³)A band that measures 210 mm³ in 14K yellow gold therefore comes out at 210 ÷ 1000 × 13.07, which is 2.74 grams.
What are the densities of jewellery alloys?
Density depends on what the gold is alloyed with, not just the karat. 14K white gold alloyed with palladium is denser than 14K yellow gold, and platinum is heavier than both. Use the figure for the alloy your caster actually pours, not a generic "gold" value.
| Alloy | Density g/cm³ | Karat | Grams per 1000 mm³ |
|---|---|---|---|
| 9K Yellow Gold (approx.)1 | 11.50 | 9K | 11.50 |
| 10K Yellow Gold2 | 11.57 | 10K | 11.57 |
| 14K Yellow Gold2 | 13.07 | 14K | 13.07 |
| 18K Yellow Gold2 | 15.58 | 18K | 15.58 |
| 24K Yellow Gold3 | 19.32 | 24K | 19.32 |
| 10K White Gold (nickel)2 | 11.07 | 10K | 11.07 |
| 14K White Gold (nickel)2 | 12.61 | 14K | 12.61 |
| 18K White Gold (nickel)2 | 14.64 | 18K | 14.64 |
| 10K Rose Gold2 | 11.59 | 10K | 11.59 |
| 14K Rose Gold2 | 13.26 | 14K | 13.26 |
| 18K Rose Gold2 | 15.18 | 18K | 15.18 |
| 18K Red Gold2 | 15.18 | 18K | 15.18 |
| 18K Green Gold2 | 15.90 | 18K | 15.90 |
| Platinum 950 (ruthenium)3 | 20.70 | 950 | 20.70 |
| Platinum 900 (iridium)2 | 21.54 | 900 | 21.54 |
| Sterling Silver 9253 | 10.36 | 925 | 10.36 |
Densities are supplier figures, not estimates. One label can cover more than one alloy, so a shop confirms or edits its own in the studio under Setup, Metals.
The two white golds are the common trap. A nickel white and a palladium white at the same karat have different densities, so a quote built on the wrong one is wrong by a margin you will notice on an invoice.
Why is the model volume different from the finished ring?
Three reasons, and each one moves the number in a predictable direction.
- Finger size. A band scales with the finger it is cut for. The same design at a larger size holds more metal, so volume has to be measured at the size being made, not at whatever size the file was drawn in.
- Stone seats. Seats, holes and pavé pockets are cut out of the metal. If the model still has solid seats, the volume is too high.
- Casting loss. Sprues, flashing and polishing remove metal after the pour. Casters usually carry their own allowance for this.
Does the file format change the answer?
Only through precision. A NURBS file such as 3DM carries exact surfaces, while a mesh format such as STL or GLB approximates curves with triangles. A coarse mesh rounds off the volume slightly. For a quote the difference is small; for a model that will be scaled and re-cut, start from the NURBS file where you have one.
Getting the volume without doing it by hand
A 3D model already contains its own volume, so the measurement does not have to be manual. Uploading the file to the studio measures the solid volume on import and applies the density for the alloy you pick, including at a different finger size. The same calculation is available over the public API if you would rather run it from your own system.
Related
- Casting loss in jewellery manufacturing
Casting loss is the metal that never reaches the finished piece: sprues, flashing and polishing. It is why a cast ring weighs less than the metal poured.
- Weight, stones and cost-based pricing
How the app measures metal weight, side stones and carat from a 3D model, and how cost-based pricing turns that into a price.
- Background, lighting and ground
Set the backdrop, the HDR environment that lights gems and metals, the ground shadow or reflection, and the advanced render controls.