Troy Ounces to Milligrams (oz t to mg)

1 troy ounce equals 31,103.4768 milligrams exactly.

1 troy ounce = 31,103.4768 milligrams

How to convert troy ounces to milligrams

To convert troy ounces to milligrams, multiply the number of troy ounces by 31,103.4768. This factor is exact. To go the other way, multiply milligrams by 0.00003215074657 (rounded).

milligrams = troy ounces × 31,103.4768

Example: 10 troy ounces = 311,034.768 milligrams.

About these units

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)

Milligram (mg)

Metric (SI)Current unit

One thousandth of a gram. Used for medicine doses and vitamins.

No single inventor can be credited with the milligram. It arrived with the metric system that France introduced in the 1790s, where the gram was the basic unit of mass and thousandths of it were named with a prefix. When the International System of Units was later built around the kilogram, the rule against stacked prefixes meant that a millionth of a kilogram is written 1 mg, never a microkilogram, so the milligram remained a gram-based unit even though the gram itself is not the SI base.

A milligram is small enough that doses of medicine and vitamins are measured in it routinely. A US penny weighs about 2.5 g, so a milligram is roughly one 2,500th of a coin. The unit is also at the center of a well-known safety problem: milligram and microgram differ by a factor of 1,000, and the abbreviation mcg for micrograms is used on prescriptions precisely so that a handwritten micro sign cannot be misread as milli. Confusing the two has caused serious medication errors.

1 milligram = 0.000001 kilograms (exactly).

Sources: Wikipedia: Milligram; Wikipedia: Microgram; Wikipedia: Gram

Related conversions

See all weight & mass units.