Gold Purity Standards Around the World: .900 to .99999 Explained

Short answer: gold purity is expressed as a decimal fineness out of 1.000 — .900 (21.6-karat) and .9167 (22-karat) are common older or durability-focused standards, .999 (three nines) and .9999 (four nines, 24-karat) are the modern investment-bullion standard, and .99999 (five nines) is an exceptional purity only a handful of products reach. Two coins of the same stated weight at different purities do not contain the same amount of actual gold, and comparing their prices without adjusting for that is a common beginner mistake.

Why Purity Varies at All

Pure (.9999 or higher) gold is soft and marks easily, which is why older coin programs and bars built for durability — like the pre-2013 Gold Britannia or the historic pre-1991 Mexican Gold Libertad — were alloyed down to 22-karat (.9167) or even 90% (.900), trading some purity for a harder, more wear-resistant coin. Modern investment-focused coins and bars generally prioritize purity instead, since they're meant to be stored rather than circulated.

The Common Fineness Tiers

• .900 (21.6-karat) — historic standard, seen in coins like the Mexican Centenario and pre-1991 Gold Libertad
• .9167 (22-karat) — the American Gold Eagle, pre-2013 Gold Britannia, and the Krugerrand all use this alloy, chosen for durability
• .999 (three nines) — the standard for most silver coins and some gold products
• .9999 (four nines) — the modern gold investment standard: Gold Maple Leaf, American Buffalo, PAMP and Valcambi bars, and most coins minted since the 2000s
• .99999 (five nines) — an exceptional tier reached by very few products, including the Canadian Call of the Wild series

Why This Matters When Comparing Prices

A 1 oz coin at .9167 fine contains meaningfully less actual gold than a 1 oz coin at .9999 fine, even though both weigh the same on a scale — the alloyed coin's "1 oz" refers to its pure gold content being exactly 1 troy oz within a heavier total coin, which is a different calculation than a single-purity bar where total weight and gold content are the same number. Always compare price per unit of actual gold content, not price per coin or price per gram of total weight, when shopping across different purity standards.

Does Higher Purity Mean "Better"?

Not automatically. Higher purity means more actual gold per unit weight and generally a slightly higher premium reflecting refining cost — but a 22-karat coin isn't a worse investment, just a different one, often chosen specifically for its added durability against scratches and handling marks. The right purity depends on your priority: maximum gold content and resale simplicity (favor .9999+) or a harder-wearing coin for long-term physical handling (22-karat alloys hold up better).

Summary

• Gold fineness is expressed as a decimal out of 1.000 — .900 up through .99999
• Lower-purity alloys (.900, .9167) trade gold content for durability
• .9999 fine is the modern standard for most investment-grade gold
• Always compare price per unit of actual gold content, not price per coin, across different purities