Learn / Purity, karats and hallmarks
Fineness and purity marks, from 999 to five nines
Fineness measures gold purity in parts per thousand. Learn what 999, 9999 and 99999 mean, why bullion bars carry these numbers and how they relate to karats.
Parts per thousand
Fineness (also called millesimal fineness) states purity as parts per thousand of pure metal by weight. A bar stamped 999.9 contains 999.9 parts gold per 1,000 parts total, or 99.99 percent. It is a more precise system than karats and is the standard language of bullion bars and coins.
The common fineness grades
| Fineness | Percent gold | Nickname | Typical use |
|---|---|---|---|
| 995 | 99.5 percent | Two nines five | Minimum for large London Good Delivery bars |
| 999 | 99.9 percent | Three nines | Many bars and some coins; often called 24K |
| 999.9 | 99.99 percent | Four nines | Most modern bullion bars and many coins |
| 999.99 | 99.999 percent | Five nines | Special issues and high-purity industrial gold |
| 916.7 | 91.67 percent | 22K | Gold Eagle, Krugerrand, traditional sovereign |
| 900 | 90 percent | Coin gold | Many older circulating gold coins, including pre-1933 US gold coins |
Four nines and five nines
Four nines (99.99 percent) became the standard for many bullion products in the late 20th century. The Royal Canadian Mint was a pioneer: its Gold Maple Leaf coin, launched in 1979 at 99.9 percent, was upgraded to 99.99 percent in 1982. In 2007 the Mint also produced special Maple Leaf coins at 99.999 percent, five nines, among the purest gold coins ever made.
For most practical purposes, the difference between 99.9 and 99.99 percent is very small in gold content. It matters more for industry, where trace impurities affect electronics, and as a marketing and quality signal for bullion.
Why 22K coins still exist
Coins such as the American Gold Eagle and the South African Krugerrand are 22K (91.67 percent). They are alloyed with copper (and in the Eagle's case some silver) to make them harder and more scratch-resistant. Importantly, a 1 oz coin of this type still contains one full troy ounce of pure gold; it simply weighs more in total, about 33.9 grams, because of the added alloy. Always check whether a stated weight refers to the gross weight or the fine gold content. See the bullion coin comparison.
Gross weight versus fine weight
- Gross weight: the total weight of the item, including alloy metals.
- Fine weight: the weight of pure gold it contains.
Fine weight = gross weight x fineness / 1,000. A 33.93 gram coin at 916.7 fineness contains 33.93 x 0.9167 = about 31.1 grams, which is one troy ounce. See the spot price and the troy ounce for why ounces are "troy".
Good Delivery bars
In the wholesale London market, large bars must meet the London Bullion Market Association (LBMA) Good Delivery standard:
- Gold content between about 350 and 430 troy ounces (roughly 11 to 13.4 kilograms), usually close to 400 oz
- Minimum fineness of 995.0
- Marks including the refiner's stamp, a serial number, the fineness and the year of manufacture
- Made by a refiner on the LBMA Good Delivery List (see smelting and refining)
Each bar's exact fine gold content is calculated from its weight and assay, so two "400 oz" bars can differ slightly in value.
Converting fineness and karats
| Karat | Fineness |
|---|---|
| 24K | 999 or higher |
| 22K | 916.7 |
| 18K | 750 |
| 14K | 583 to 585 |
| 10K | 417 |
| 9K | 375 |
The full table, with uses for each karat, is in karats explained.
Reading a bar's stamp
A typical small bullion bar might show:
- The refiner's or mint's name and logo
- The weight, such as 1 OZ, 100 G or 1 KILO
- The words FINE GOLD
- The fineness, such as 999.9
- A unique serial number, often matched to an assay certificate
A stamp is a claim, not proof. Fakes can carry convincing stamps too. See how to spot fake gold.
