Grams and troy ounces
Jewellers weigh in grams. Bullion markets quote in troy ounces, an old unit that survived because the trade kept it: one troy ounce is 31.1035 grams, about ten percent heavier than the kitchen ounce. When you see "gold at $2,400 an ounce" that is the troy ounce, and dividing by 31.1035 gives the price per gram of pure gold.
The second thing the reference price assumes is purity: it is quoted for fine gold, 999.9. A piece of 18K contains 75 percent gold, so its metal value per gram is 75 percent of the fine price.
Why bars and coins follow the reference
A minted bar or a bullion coin is a standardised lump of fine gold. Its weight is stamped, its purity is guaranteed, and it does nothing else. Its value is therefore the metal value plus a premium that covers minting, packaging, distribution and the dealer's margin; small bars carry a higher premium per gram than large ones because the fixed costs are spread over less metal.
The metal price changes every trading day, sometimes every hour. A shop that printed a fixed bar price would be either overcharging or losing money by the afternoon. That is why bars and coins at DiOro999.9 show the latest listed price and are confirmed at order: when we confirm your order request, we quote the day's figure and you decide.
Why jewellery does not
A ring is not a lump of metal. It is a design, alloyed, cast or forged, finished, set, polished and hallmarked. Most of what you pay for in a set ring is the stones and the work; even in a plain band the making is a real share of the price. Jewellery is therefore priced per piece, the price holds from day to day, and it does not move with every tick of the market. The metal value is a floor under it, not the whole of it.
A worked example
The numbers below are round figures for the sake of the arithmetic, not a quote.
Suppose the reference price is $2,400 per troy ounce. Per gram of fine gold that is 2,400 divided by 31.1035, about $77.17. A 20 g bar of 999.9 contains 20 g of fine gold, so its metal value is about $1,543. Add a premium of, say, 4 percent and the bar is offered around $1,605. Tomorrow, with the reference at $2,350, the same bar is about $1,572: same metal, different day.
Now a 4.1 g band in 18K. Its fine gold content is 4.1 times 0.75, about 3.08 g, worth about $237 at the same reference. The band is listed at $520, because the other $283 is the making, the hallmarking and the margin. When the reference moves a few percent, the band's price does not move at all.
What this means when you order
For jewellery and watches the price you see is the price you pay, plus shipping. For bars and coins the listing shows the latest price and our confirmation gives you the day's figure before anything is charged; if you prefer to wait for a different day, say so and we hold the request. None of this is investment advice. If you are buying metal as an investment, talk to a licensed adviser first.