- Millesimal fineness is gold content in parts per thousand: 585 = 58.5% pure gold; karats convert as karat ÷ 24 × 1000.
- Metal value of an item = weight × (fineness ÷ 1000) × price per gram of pure gold.
- For investment only pure-gold content and the buy-sell spread matter — which is why bars are 999.9 fine.
How the system works
Millesimal fineness states pure-gold content in parts per thousand: a 585 alloy holds 585 grams of gold per kilogram. The karat scale (24K = pure gold) is common in English-speaking markets; conversion is karat ÷ 24 × 1000.
Purity table with live per-gram value
| Fineness | Karat | Gold content | Gold value in 1 g | Typical use |
|---|---|---|---|---|
| 999.9 | 24K | 99.99% | $129.21 | Investment bars and coins |
| 958 | 23K | 95.80% | $123.8 | British crown gold, rare pieces |
| 916 | 22K | 91.60% | $118.37 | Bullion coins (Krugerrand, Sovereign), jewellery across Asia and the Middle East |
| 750 | 18K | 75.00% | $96.92 | Premium jewellery |
| 585 | 14K | 58.50% | $75.6 | Mass-market jewellery in Europe and the CIS |
| 375 | 9K | 37.50% | $48.46 | Budget jewellery |
Priced off the live $129.22 per gram of 999.9 (Gold API, indicative spot). This is the value of contained gold, not a retail price.
Pricing any item
Formula: weight × (fineness ÷ 1000) × price per gram of pure gold. A 4 g ring of 585 contains 4 × 0.585 = 2.34 g of pure gold — multiply by the current gram price in your currency (see prices by currency) or use the gold calculator.
Purity and investing
Investment products (bars, bullion coins) are made of 999.9 or 916/900 gold with transparent market-linked pricing. Jewellery almost always loses as an investment because of retail premiums and buy-back discounts — the cost structure is covered in ways to buy gold.
Frequently asked questions
Is 585 (14K) gold good?
A 585 alloy contains 58.5% pure gold; the rest is alloying metal that makes it harder. Pieces are cheaper and more durable than 750/18K but contain notably less gold. For investment purposes only the pure-gold content and the buy-sell spread matter.
How do I convert karats to fineness?
A karat is a 24th share of gold in the alloy: fineness = karat ÷ 24 × 1000. So 18K = 750, 14K ≈ 583–585, 9K = 375.
Why does jewellery cost more than the gold in it?
Retail adds fabrication, brand and margin, often plus VAT; buy-back happens below the metal value. The round-trip gap can reach tens of percent for jewellery versus single percent for investment bars.
More guides
Updated: 2026-07-19. This material is informational and not investment advice — see the disclaimer. Data provenance is described in the methodology.