Gold Impurity Calculator (Grams) — Alloy Content & Refining Estimate
A gold impurity calculator works backwards from the karat purity stamp — given gross weight and karat, it returns the alloy (impurity) mass that will be lost during refining to pure 999.9 gold. For a 50 g 22K ring, the impurity mass is 50 × (2 ÷ 24) = 4.167 g; only 45.833 g pure gold will emerge from the refining process.
This calculation is the foundation of pre-refining valuation. Refiners pay you for pure gold yielded, not gross weight handed over. The impurity mass becomes by-product (typically copper, silver and zinc), which is sold separately and credited at a much lower rate.
Impurity content math
Impurity (g) = Gross grams × (24 − karat) ÷ 24. Pure gold (g) = Gross grams × karat ÷ 24. Refining loss = up to 1% on top of stated alloy mass, depending on refiner process.
Sample conversions
| Input | Result |
|---|---|
| 10 g of 24K (999) | 0.01 g impurity (≈0.1%) |
| 10 g of 22K (916) | 0.833 g impurity (8.33%) |
| 10 g of 18K (750) | 2.500 g impurity (25%) |
| 10 g of 14K (583) | 4.167 g impurity (41.67%) |
When to use this calculator
- Pre-refining valuation — know exactly how much pure gold to expect back.
- Scrap dealer negotiation — verify the refiner's impurity claim against the karat stamp math.
- Alloy-by-product accounting — track separately for tax/inventory purposes.
Frequently asked questions
Why is "impurity" different from "refining loss"?
Impurity is the predictable alloy mass per the karat ratio (e.g., 8.33% of 22K). Refining loss is the additional uncertainty (~0.5-1%) from oxidation, crucible spill and dust — on top of the impurity mass.
Are the alloy metals worth anything on resale?
Yes — copper, silver and small palladium yields are sold separately by the refiner. Most pre-pay refiners include a small credit for these in the gross settlement; pay-after-refine deals show them as a line item.