Inputs
Starting mass and two fineness valuesMass balance · no guesswork
Gold Alloy Mixing Calculator
Enter a starting mass, its known fineness, the target fineness, and the added alloy's fineness. The tool solves a mass-balance equation and rejects targets that a mixture of the two materials cannot reach.
Mass balance · no price input required
DeterministicExact mass-balance equationEquation
m₂ = m₁(fₜ − f₁) ÷ (f₂ − fₜ)Fail-closed
Impossible targets return a clear errorSpecification and intent
The target must lie between the two material finenesses
Mixing materials can only produce a final fineness between the starting material and the added alloy. The equation solves added mass directly; it does not recommend a recipe or identify unknown scrap.
Interactive tool
Solve the alloy mass balance
Enter fineness in parts per thousand from 0 to 1,000. Use 0 for a gold-free added alloy only when that describes the material.
Required added material28.205128 gNegative mass is never returned.
Final total mass128.205128 gStarting mass plus added material.
Calculated final fineness585.000‰Recomputed from the mass-balance equation.
Gold mass is conserved: m₁f₁ + m₂f₂ = (m₁ + m₂)fₜ. The target must be between the starting and added-material fineness, unless it already equals the starting fineness (zero addition). Process loss and assay error are excluded.
Calculation method
How the result is calculated
Gold mass is conserved: m₁f₁ + m₂f₂ = (m₁ + m₂)fₜ. Rearranging gives m₂ = m₁(fₜ − f₁)/(f₂ − fₜ).
This ideal mass-balance result excludes process loss, oxidation, contamination, solder, assay error, and refining practice. It is not metallurgical or safety advice.
Evidence and references
Specification sources
Primary references where available
Information only, not investment advice. Theoretical metal value is not a dealer offer, retail price, jewelry appraisal, assay, or guaranteed sale price.