Troy Ounce (oz t)

Troy & apothecaries'Current unit

Exactly 31.1034768 g (480 grains). The standard unit for precious metals; gold and silver prices are quoted per troy ounce.

1 troy ounce = 0.0311034768 kilograms (exactly).

About the troy ounce

Nobody is certain where troy weight got its name. The usual explanation is the fairs of Troyes in France, where English merchants traded by the early 9th century, and the word troy appears in English in 1390. An alternative theory ties it to a word for weighing by balance, though it is unsourced. Troy weights were first used in England in the 15th century and made official for gold and silver in 1527. The British Imperial troy ounce was adopted in 1824 and became the basis for US coinage through an act of Congress in 1828.

The troy ounce is exactly 31.1034768 g, or 480 grains, about 9.7 percent heavier than the ordinary avoirdupois ounce. A troy pound has only 12 ounces and is lighter than the avoirdupois pound, a mismatch that catches many first-time bullion buyers. Troy ounces remain the standard in precious-metal markets, even in countries that otherwise use SI, so gold, silver and platinum prices are all quoted per troy ounce. In the UK it is the only troy unit still permitted in trade, and only for precious metals.

Sources: Wikipedia: Troy ounce; Wikipedia: Ounce; NIST Guide to the SI, Appendix B.8 (mass conversions)

Troy Ounce conversion chart

1 troy ounce expressed in every other weight & mass unit:

More Troy & apothecaries' units

• troy pound (weight & mass)
• pennyweight (weight & mass)
• scruple (weight & mass)
• apothecaries' dram (weight & mass)

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