Gold Purity Explained: Karats & Fineness
Two numbers describe how much actual gold is in a piece: karats and fineness. Both are everywhere — on jewelry stamps, bullion bars and dealer quotes — and mixing them up is the fastest way to misjudge a price.
Karats: parts out of 24
Pure gold is 24 karat (24K). Karats divide the piece into 24 parts: 18K means 18 parts gold out of 24 (75%), with the rest other metals. Fewer karats, less gold:
| Karat | Fineness stamp | Gold content | Common use |
|---|---|---|---|
| 24K | 999 / 999.9 | 99.9% | Bullion bars & coins |
| 22K | 916 | 91.7% | High-purity coins, some jewelry |
| 18K | 750 | 75.0% | Fine jewelry |
| 14K | 585 | 58.3% | Everyday jewelry (very common in the U.S.) |
| 10K | 417 | 41.7% | Budget jewelry (U.S. legal minimum to be called gold) |
| 9K | 375 | 37.5% | Budget jewelry (common in the UK) |
Fineness: parts per thousand
Bullion traders prefer fineness — the parts-per-thousand measure. A bar stamped 999.9 (read "three nines fine" or "four nines") is 999.9 parts gold per 1,000. The stamps map directly to karats: 999 ≈ 24K, 916 ≈ 22K, 750 ≈ 18K, 585 ≈ 14K, 417 ≈ 10K.
Why isn't all gold 24K?
Pure gold is soft. It scratches, dents and bends, which is fine for a bullion bar you store and useless for a ring you wear daily. Jewelers alloy gold with copper, silver, palladium or nickel to add hardness — and in the case of rose or white gold, different colors. Bullion, by contrast, is investment metal: it wants maximum purity, so bars and most bullion coins are 24K or 22K.
What purity means for value
The melt value of any piece is simply: weight × fineness × spot price. An ounce of 18K does not contain an ounce of gold — it contains three-quarters of an ounce. That's why dealers test purity before quoting, and why two identical-looking rings can differ 40% in value. Try the math yourself with our gold calculator.
Reading stamps and hallmarks
- Numbers — 999, 916, 750, 585, 417, 375 are fineness stamps; "18K" or "14K" is the karat equivalent.
- Maker's mark — identifies the manufacturer or assay office.
- When in doubt — reputable dealers verify with electronic testers or XRF analysis, not just the stamp.
Next: see how purity plays into pricing in How Gold Is Priced, and check the live gold price today.