One word, two measures
An ounce is not a complete description of mass unless its system is clear. Precious metals commonly use the troy ounce, equal to exactly 31.1034768 grams. The ordinary avoirdupois ounce equals exactly 28.349523125 grams. That makes a troy ounce about 9.7 per cent heavier. NIST's measurement tables distinguish the units explicitly, while LBMA uses the troy ounce in precious-metals markets. A household conversion based on the ordinary ounce can therefore produce the wrong result when applied to a silver quotation.
Let the units do the work
To convert grams to troy ounces, divide by 31.1034768. A kilogram contains approximately 32.15075 troy ounces. To travel in the opposite direction, multiply the number of troy ounces by 31.1034768. Keep additional digits while calculating, then round the displayed answer to a useful precision. A clear label such as grams or troy ounces is more valuable than a long decimal without a unit. The conversion changes how a mass is expressed; it does not change the amount of metal.
Weight is not purity
Now consider a hypothetical piece containing 100 grams of metal at exactly 925 fineness. Its total metal mass is approximately 3.2151 troy ounces, but its fine-silver content is only 92.5 grams. Those are different measurements answering different questions. For a coin or bar, read whether the stated weight describes gross metal weight or the guaranteed quantity of fine silver. Do not automatically apply a purity adjustment twice if a product already states its fine-metal content. Product specifications determine what a particular label promises.
Make prices comparable
Before comparing two prices, align their currency, unit and purity basis. A price per gram cannot be compared directly with one per troy ounce. Nor is a wholesale reference quotation necessarily the price of a finished retail object. Conversion provides the common measuring scale; premiums, fabrication costs and selling terms still need separate treatment. Keeping those steps distinct makes the arithmetic easy to check and prevents an innocent-looking unit label from changing the conclusion.
Sources & further reading
- NIST · Handbook 44, 2024, Appendix C: General tables of units of measurement ↗
- LBMA · The troy ounce ↗
Sources checked 14 November 2026. Reference organisations do not endorse this website. Price examples are hypothetical and educational.