18ct gold has a nominal gold fraction of 18/24, or 750 parts per thousand. The reference here measures theoretical metal content per net gram of alloy. A branded ring’s purchase invoice can include fabrication and design costs that a scrap buyer does not repay. Compare the full item quote, not just its gold fraction, before deciding whether two offers use the same basis.
Fine-metal formula
Quantity × 1 g × 0.75 × fine-gram reference
Fine-gram reference = USD/troy ounce ÷ 31.1034768 × daily reference FX. Fineness is never applied twice.
750 gold and net weight
A net alloy weight of 10 grams at 750 fineness contains a theoretical 7.5 grams of gold. This weight illustration is not a current dealer price or an assay result. Remove stones and other materials from the calculation basis.
Resale and retail are different
A retail ask prices a finished product. A buyer’s bid may instead reflect an assessed metal quantity and processing costs. The difference cannot be inferred from the spot reference alone.