Metal Alloy Mixing Calculator
Calculate precise metal alloy ratios for gold karat blending, silver sterling mixes, and custom jewelry alloys.
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.