Work out silver purity converter instantly with clear inputs, formula shown and shareable results.
Silver purity is quoted as fineness in parts per thousand rather than in karats. Sterling silver is 925 - 92.5% silver with 7.5% copper - so a 50 g sterling item holds 46.25 g of silver. Britannia silver is 958 and fine silver 999, which is too soft for tableware but used for bullion.
Purity
fraction = fineness / 1000
Silver content
mass of silver = item mass x purity
Because 7.5% copper adds the hardness and durability that pure silver lacks, while keeping the colour and tarnish behaviour acceptable.
Yes. Copper drives tarnish, so higher fineness tarnishes more slowly. Argentium alloys replace some copper with germanium to reduce it further.