Gold Karats and Purity: 24K, 22K, 18K, 14K Explained
Karat (K) expresses how many parts out of 24 are pure gold. Fineness expresses the same thing in parts per thousand. Both describe weight, not volume or colour.
Published by the Heartline Works team · Last reviewed 2026-10-02 · Editorial policy
Karat, fineness and percentage
| Karat | Gold share | Common fineness mark |
|---|---|---|
| 24K | 100% nominal (≥ 99.9%) | 999 / 995 |
| 22K | 91.67% | 916 / 917 |
| 21K | 87.5% | 875 |
| 18K | 75% | 750 |
| 14K | 58.33% | 585 |
| 10K | 41.67% | 417 |
| 9K | 37.5% | 375 |
Formula: karat ÷ 24 = gold share. 750 fineness means 750 parts per 1,000 are gold.
Why the rest of the alloy matters
The remaining metal (copper, silver, zinc, palladium and others) sets colour and hardness. Two 18K pieces can have different colours and slightly different densities, which is why density-based tools can only estimate.
Pure gold content
A 10 g piece of 22K contains 10 × 22 ÷ 24 ≈ 9.17 g of pure gold. That figure, not the gross weight, is what the reference value is based on.
Hallmarks
Hallmarking rules differ by country. A hallmark is a claim backed by a testing body; the number on a piece without a recognised hallmark is only a stamp. Assay testing is the way to confirm purity.
Try the tools
- Karat & Purity Calculator — Convert between karat, fineness and percent; see pure-gold content of any weight.
- Gold Value Calculator — Reference value of gold by weight and purity, with pure-gold content.