14K, 18K and 22K gold weight: from volume to grams
The weight of a piece comes from two numbers: the volume of the metal and the density of the alloy. With the volume in cubic millimeters (mm³) and the density in grams per cubic centimeter (g/cm³):
weight (g) = volume (mm³) ÷ 1000 × density (g/cm³)
The same model is heavier in 22K than in 14K, because the alloy gets denser as the gold content rises. Stones are not part of this calculation; it is the weight of the metal.
Alloy densities
These are the values the Kumpix engine uses for weight. The density of a real alloy varies a little with its mix; after casting, the scale has the final word.
| Metal | Density (g/cm³) | Casting shrinkage |
|---|---|---|
| 22K Gold | 17.5 | 1.45% |
| 18K Gold | 15.5 | 1.60% |
| 18K White Gold | 15.6 | 1.70% |
| 18K Rose Gold | 15.2 | 1.60% |
| 14K Gold | 13.0 | 1.75% |
| Platinum 950 | 21.4 | 2.20% |
| 925 Silver | 10.4 | 2.00% |
Example: a comfort-fit band
The Kumpix engine measured the metal volume of a comfort-fit band, 4 mm wide, 1.7 mm thick, TR 14 (inside diameter 17.20 mm), at 373.9 mm³. In 14K that is 373.9 ÷ 1000 × 13.0 ≈ 4.86 g; in 18K it is 5.80 g and in 22K 6.54 g.
Measured examples
| Model | Volume (mm³) | 14K | 18K | 22K |
|---|---|---|---|---|
| Comfort-fit wedding band, 4 mm wide, 1.7 mm thick, TR 14 | 373.9 | 4.86 g | 5.80 g | 6.54 g |
| Solitaire ring, 0.50 ct, 4 prongs, TR 14 | 204.0 | 2.65 g | 3.16 g | 3.57 g |
| Letter necklace, 14 mm, 1.2 mm thick | 83.6 | 1.09 g | 1.30 g | 1.46 g |
Casting shrinkage
Metal shrinks slightly as it cools, so a model sent to casting has to be scaled up by the shrinkage of its metal; Kumpix scales the casting STL by the value in the table. The weight, on the other hand, is calculated from the volume of the finished piece.
Weight in Kumpix
Kumpix measures the metal volume on the exact geometry and shows side by side what the same model weighs in each metal; when you change a dimension, the weight updates right away. Details are on the weight and stone report page; ring sizes and their inside diameters are in the ring size chart.