Metal-content value starts with weight, purity and price units
Weight alone does not determine the metal content’s value. Establish how much pure metal is present and what unit the entered price uses, then distinguish the arithmetic from a dealer’s offer.
Purity is a share of the weight
LBMA explains that 18-carat gold corresponds to fineness 750 per thousand, or 75%. Do not enter 18 into a field asking for a purity percentage: they express content on different scales.
The calculation cannot authenticate a hallmark or test composition. Use reliable information about the actual metal, and do not count stones or unrelated components as pure-metal weight.
References: LBMA — Purity of gold
Align weight and price units
A troy ounce is not an ordinary avoirdupois ounce. NIST lists approximately 31.10348 g for troy and 28.34952 g for avoirdupois. An ambiguous unit changes the answer even when multiplication is correct.
Record the price source, date, currency and whether it applies per gram, kilogram or troy ounce of pure metal. This calculator neither fetches today’s price nor grants rights to redistribute market data.
References: NIST SP811 Appendix B.8 — Troy and avoirdupois ounces
Content value is not a dealer quotation
LBMA’s guide distinguishes a reference market price from the metal price in jewellery or a small bar. Product form, fineness and size can involve premiums or discounts.
The result here is calculated content value without fabrication charges, collectible value, dealer discounts or tax. Compare written offers on the same basis; a difference alone does not establish that an offer is wrong or that selling is suitable.
References: LBMA — The price and physical product differences
A stated fictional price, not today’s quote
A fictional item with metal weight 20 g and purity 75% contains 15 g of pure metal. At an educational assumed price of 100 currency units per pure gram, its content value is 1500.
The price 100 is chosen for arithmetic, not quoted for gold or silver. Changing purity to 90% with the same weight and price gives 18 g and 1800; the calculator cannot determine which purity describes your item.