Per Mille (Fineness)
Also: Parts per thousand, Millesimal fineness, Thousandths
Per mille (parts per thousand) expresses the fineness of a precious metal as the proportion of pure metal in the total mass and is the legally binding figure stamped on bars and coins.
Per mille (parts per thousand) is the unit used to describe the fineness of a precious metal. It states how many thousandths of the total mass consist of the pure metal. A gold bar marked 999.9 therefore contains 999.9 out of every 1,000 units of weight as pure gold - the remainder being unavoidable trace elements. The per-mille figure is internationally standardised (ISO 9202) and has largely replaced older carat markings on bars and industrial products.
Formula: calculating fine weight
Fine weight = Gross weight x (fineness / 1000)
Example: a 100 g bar at 585 parts contains 100 g x 0.585 = 58.5 g of fine gold. You can work out the melt value directly using the melt value calculator.
Common finenesses at a glance
| Fineness (per mille) | Carat equivalent | Metal | Typical use |
|---|---|---|---|
| 999.9 | - | Gold | Investment bars (four nines) |
| 999 | 24 carat | Gold | Coins (e.g. Maple Leaf, Panda) |
| 958 | - | Silver | Britannia silver (UK) |
| 950 | - | Platinum/palladium | Investment bars, jewellery |
| 925 | - | Silver | Sterling silver (jewellery, cutlery) |
| 916 | 22 carat | Gold | Krugerrand, Sovereign |
| 835 | - | Silver | Historical coins |
| 800 | - | Silver | Historical coins |
| 750 | 18 carat | Gold | High-quality jewellery |
| 585 | 14 carat | Gold | Common European jewellery |
| 375 | 9 carat | Gold | British jewellery |
| 333 | 8 carat | Gold | Lowest German jewellery grade |
The gold price and silver price always refer to metal of 999.9 fineness - at a lower fineness the material value falls in proportion.
Per mille versus carat
The carat system for gold is the older, English-speaking convention. The conversion is exact:
Fineness (per mille) = carat x 1000 / 24
So 24 carat corresponds to 1,000 parts (theoretically pure gold) and 18 carat gives exactly 750 parts. Across the European single market the per-mille figure is the binding statement; the carat value may be shown as an addition.
Hallmarking and legal meaning
To qualify as investment gold, bars and coins must meet minimum fineness thresholds set by EU VAT rules that Ireland applies: gold bars need at least 995 (99.5%) and gold coins at least 900 (90.0%), where the coin was minted after 1800 and is or was legal tender in its country of issue. These thresholds carry weight for VAT: investment gold that meets them is exempt from VAT in Ireland, whereas lower-grade jewellery or semi-finished goods are not. (Not tax or legal advice - consult a qualified adviser for binding guidance.)
The hallmark - the engraved or stamped fineness mark - on a piece of jewellery or a bar is the visible proof of the per-mille value. Independent assay offices and refineries such as Heraeus or Umicore guarantee compliance with the stated fineness through their maker's mark.
Practical tip: buying and melt value
When selling gold, the payout is always based on the fine weight, not the gross weight. Anyone selling old jewellery gold (e.g. 585) will receive correspondingly less than for an investment bar (999.9). The Buying Price Calculator lets you estimate a realistic return in advance.
In brief
Per mille is the universal, legally defined language of the bullion trade: the higher the value, the greater the pure-metal content and the closer the material value sits to the current spot price. For bars and investment coins, only 999 and above is worth buying - anything below contains alloying metals that must be deducted when refined.