GemDiagram Docs

Reports & Export: Size/Yield Calculator

The Size/Yield Calculator helps you estimate the finished stone size and weight based on your rough gemstone dimensions, material, and design's yield.

When you use it

You have:

  • A piece of rough with known dimensions (length, width, height in mm).
  • A design (the facet count and proportions from your .facet file).
  • A question: "How big will the finished stone be, and how much will it weigh?"

The calculator answers this by:

  1. Computing the design's theoretical volume.
  2. Applying a yield percentage (how much of the rough becomes the finished stone).
  3. Multiplying by the material's density to get the weight.

Inputs

  • Rough dimensions: Length, width, height in mm.
  • Material: The gemstone type (sets the density).
  • Yield %: What percentage of the rough becomes the finished stone (e.g., 40%). If you've run the Rough Planner, use the yield it calculated. Otherwise, use 30–50% as a typical range depending on complexity.
  • Girdle diameter: The width of the finished stone (in mm). This is usually derived from the rough width, scaled by the yield.

Outputs

  • Rough weight: Estimated weight of the uncut rough.
  • Yield: The percentage that survives as finished stone.
  • Finished weight: The estimated carat weight after cutting and polishing.
  • Finished dimensions: Approximate length, width, height of the finished stone.

Accuracy

The estimate is rough — it assumes:

  • The design volume is accurate (it usually is, from the Developer geometry).
  • No unexpected breakage.
  • No major regrinding (slight size loss is normal).
  • Uniform density (no large voids or inclusions).

The actual finished weight will likely be 5–20% lower than the estimate due to polish dust loss and minor regrinding.

Using it for planning

Jewelry designers often work backward from a desired carat weight:

  • "I need a 2-carat Ruby."
  • Enter 2 carats as the target finished weight.
  • The calculator shows how large the rough needs to be.

Use it as a planning tool before you buy the rough, or as a verification tool before you start cutting.

Alternatives

If you have a specific rough stone, the Rough Planner is more powerful — it searches many orientations to find the maximum yield for your exact rough. The Size/Yield Calculator is simpler and doesn't require a rough shape model — it just uses dimensions.

See Rough Planner: Best-Yield Overview for a full orientation search.