Carats to Troy Ounces (ct to oz t)

1 carat equals 0.006430149314 troy ounces (rounded).

1 carat = 0.006430149314 troy ounces

How to convert carats to troy ounces

To convert carats to troy ounces, multiply the number of carats by 0.006430149314. The factor is rounded to 10 significant digits. To go the other way, multiply troy ounces by 155.517384.

troy ounces = carats × 0.006430149314

Example: 10 carats = 0.06430149314 troy ounces.

About these units

Carat (ct)

Metric (SI)Current unit

Exactly 200 milligrams. The unit for weighing gemstones such as diamonds. Not to be confused with the karat, a measure of gold purity.

Jewellers once weighed stones against seeds. The word carat traces back to the Greek keration, meaning a carob seed, and reached English through Italian and Arabic. Carob seeds were used as balance weights for gems and gold, though their mass varies about as much as any seed does. Before 1907 each country had its own carat, ranging from roughly 187 to 216 milligrams. It was used for gold early on and for diamonds from the 1570s. An international carat of 205 mg was proposed in Paris in 1871, but the 200 mg metric carat won out.

The metric carat was adopted at the Fourth General Conference on Weights and Measures in 1907. France made it mandatory, the United States followed in 1913 and the United Kingdom in 1914. Today it is exactly 200 mg, so five carats make a gram, and it is divided into 100 points of 2 mg each; a diamond described as 25 points is a quarter carat. Carat is used for gemstones and pearls, and it should not be mixed up with karat, which measures the purity of gold and is a separate idea.

1 carat = 0.0002 kilograms (exactly).

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

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.

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.

1 troy ounce = 0.0311034768 kilograms (exactly).

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

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