What Does 750 Mean on Gold?

The 750 mark is the international signature of fine jewellery. Inside the shank of a sapphire ring, on the clasp of a designer necklace or the back of a rose gold watch case, those three digits make the same claim everywhere in the world: this metal is 18-karat gold.

The Arithmetic Behind 750

Purity in the modern trade is written as fineness, parts of gold per thousand parts of metal. Eighteen karat means 18/24ths gold, and 18 ÷ 24 = 0.75 exactly. So 18K gold is 750 parts per thousand, or 75% pure, and "750" is stamped rather than "18K" in most of the world. The two notations are interchangeable; the conversion for every grade appears in our karat versus fineness guide.

Why 750 Appears on Fine Jewellery

18K is the purity at which gold becomes strong enough for precision work while remaining three-quarters pure. Slim prongs hold sapphires securely, hinges and clasps keep their spring, and engraving stays crisp, which is why gem-set jewellery, including most of Sri Lanka's export sapphire work, is made in 18K gold. The mark therefore appears most often on exactly the pieces where a buyer has the most at stake.

One Mark, Three Colours

A 750 stamp says nothing about colour. Yellow, white and rose gold at 18K all carry the same mark, because fineness measures gold content, not appearance. The remaining 25% of the alloy is what differs: whitening metals such as palladium in white gold, copper-rich mixes in rose gold. Rhodium plating on white gold sits on top of the alloy and does not affect the fineness claim.

A Claim, Not a Guarantee

As with the 916 mark on traditional jewellery, a 750 punch is applied by the maker and certifies nothing by itself. Some countries operate independent hallmarking systems in which an assay office verifies fineness before marking; elsewhere, including in much day-to-day practice, the stamp stands alone. Marking practices vary between makers and markets, so the reliable protections are the same everywhere: a reputable seller, the fineness written on the invoice, and for significant pieces an independent test or assay report.

Checking and Valuing 750 Gold

XRF machines read an 18K alloy in seconds without damage, and touchstone or acid tests remain common at the counter, see our overview of gold testing. On value, remember the metal is 75% gold: a 750 piece's melt value is three-quarters of the pure-gold rate for its weight, which you can check against the day's figures using the gold purity calculator. The rest of the price lies in making and stones, worth paying for, but worth seeing itemised on the invoice, line by line, before you commit to a significant purchase.