Bullion purity explained: what .9999 and 999.9 mean

Bullion purity is normally expressed as fineness: parts of pure metal per thousand. The same purity can be written in several ways:

A product stamped “999.9” and one described as “.9999 fine” or “99.99% pure” have the same purity.

Investment gold bars and many modern bullion coins are refined to 999.9 fineness. Some refiners also produce 999.99 (“five nines”) products.

Certain well-known gold coins are 22 carat (916.7). The other 8.33% is typically copper or silver, which makes the coin harder wearing. These coins are made slightly heavier so that they still contain their stated weight of pure gold, for example one troy ounce.

Investment silver is typically 999 or 999.9 fine. Sterling silver (925) is used for jewellery and silverware and is not generally treated as investment bullion.

What ultimately matters is the fine metal content: the weight of pure gold or silver a product contains. It equals the product’s total (gross) weight multiplied by its purity.

HLBullion product pages list metal, weight and purity where they are recorded, so products can be compared on a like-for-like basis. See how weights work.