Metal Alloy Mixing Calculator
Calculate metal alloy ratios for gold karat blending and custom jewelry.
Returns grams of fine metal and alloy for yellow, white, and rose gold recipes.
Jewelry alloy mixing requires precise calculations to achieve a target purity. The most common application is blending gold of different karats or mixing pure gold with base metals.
The Karat System: Pure gold is 24 karat (24K). Each karat represents 1/24th (4.167%) gold content.
- 24K = 99.9% gold
- 18K = 75.0% gold
- 14K = 58.3% gold
- 10K = 41.7% gold
Mixing Formula (two metals of different purities): To find how much of Metal A and Metal B to combine for a target purity:
Weight_A × Purity_A + Weight_B × Purity_B = Total_Weight × Target_Purity
If you know the total desired weight and one source purity: Weight_A = Total × (Target - Purity_B) / (Purity_A - Purity_B) Weight_B = Total - Weight_A
Worked Example: Making 10g of 14K gold from 24K and 10K:
- Target purity: 58.33%
- Metal A (24K): 99.9% gold
- Metal B (10K): 41.7% gold
- Weight_A = 10 × (58.33 - 41.7) / (99.9 - 41.7) = 10 × 16.63 / 58.2 = 2.86 g of 24K
- Weight_B = 10 - 2.86 = 7.14 g of 10K
Verification: (2.86 × 0.999) + (7.14 × 0.417) = 2.857 + 2.977 = 5.834 g pure gold. 5.834 / 10 = 58.34% → 14K confirmed
Common Alloy Compositions:
| Alloy | Gold | Silver | Copper | Other |
|---|---|---|---|---|
| 18K Yellow | 75% | 12.5% | 12.5% | , |
| 18K Rose | 75% | 2.8% | 22.2% | , |
| 18K White | 75% | , | — | 25% Pd/Ni |
| 14K Yellow | 58.3% | 14.2% | 27.5% | , |
| Sterling Silver | , | 92.5% | , | 7.5% Cu |
The calculator below uses the two-source mixing formula. Enter both source purities (as karat or percentage) and your desired target.
How we build and check this calculator
This calculator runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
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