Casting Shrinkage Compensation Calculator
Convert a castable pattern dimension to the dimension after casting for Au 585, Ag 925, Au 9K and Au 18K, free, no registration.
Why does the pattern need to be bigger?
Every metal alloy shrinks as it solidifies in the mould. A pattern printed or modeled in CAD has to be scaled up by the right factor first, otherwise the finished cast piece comes out noticeably smaller than planned. This calculator does the math both ways.
| EU size | Inner diameter (mm) | Pattern dimension (mm) |
|---|---|---|
| 48 | 15.28 | 15.523 |
| 49 | 15.60 | 15.847 |
| 50 | 15.92 | 16.170 |
| 51 | 16.23 | 16.494 |
| 52 | 16.55 | 16.817 |
| 53 | 16.87 | 17.140 |
| 54 | 17.19 | 17.464 |
| 55 | 17.51 | 17.787 |
| 56 | 17.83 | 18.111 |
| 57 | 18.14 | 18.434 |
| 58 | 18.46 | 18.757 |
Inner diameter is calculated as circumference (EU size in mm) divided by π. The pattern column applies the shrinkage factor of the selected alloy.
Casting shrinkage in practice
Casting shrinkage is the reduction in metal volume as it moves from a liquid to a solid state. In jewelry, it matters directly with lost-wax or lost-resin casting: a 3D-printed pattern at 1:1 scale casts into a piece a few tenths of a millimeter smaller, which on a ring can mean a genuinely different size.
The shrinkage factor depends on the alloy. Sterling silver (925) shrinks less (x1.016) than 14K gold (585, x1.0196), while 9K and 18K gold sit at their own intermediate values based on how much base metal is alloyed in. There is no universal multiplier, each alloy has to be calculated separately.
At AEJaCA we apply these exact factors on every lost-resin cast project, from rings to display pieces. A CAD model or 16K-resolution print arrives sized to the final dimension, and we automatically scale the castable pattern by the correct percentage before it goes into the mould.
Frequently asked questions
What is casting shrinkage?+
It is the reduction in metal dimensions as it solidifies inside the casting mould, after melting and filling the cavity left by the burned-out or dissolved pattern. The effect is most visible on precise elements like bands or stone settings.
Why is the shrinkage factor different for each alloy?+
Every alloy has a different metal composition (Au, Ag, Cu, Zn and other additions), which changes its solidification temperature and the density difference between liquid and solid states. That is why Ag 925, Au 9K, Au 14K (585) and Au 18K each shrink by a different amount.
How do I apply shrinkage compensation in CAD or a slicer?+
Model or import the pattern at the final target dimension, then scale it uniformly (Scale, not per-axis) by the factor for the chosen alloy, e.g. x1.016 for Ag 925. Print the result as a castable pattern and send it for casting.
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Jewelry without stones
Bands, signet rings and pendants in plain metal.
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We model in CAD, scale by the shrinkage factor, and cast in lost-resin, from design to finished piece.
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