What Is a Troy Ounce?

What Is a Troy Ounce?

Let me explain what a troy ounce is—it's a unit of measurement specifically for weighing precious metals and gems, dating back to the Middle Ages. It originated in Troyes, France, and one troy ounce equals 31.1034768 grams, as per the U.K. Royal Mint.

You might confuse it with the standard ounce, also called avoirdupois ounce, which we use for everyday items like sugar or grain. That one weighs 28.35 grams, making it slightly less than a troy ounce.

Today, the troy ounce remains the standard in the precious metals market to maintain purity standards. You'll see it abbreviated as 't oz' or 'oz t'.

Key Takeaways

Here's what you need to know: the troy ounce is the metric for weighing precious metals, equaling 31.1034768 grams. A standard ounce is 28.349 grams, about 10% less. A troy pound consists of 12 troy ounces and is lighter than a standard pound, which equals 14.6 troy ounces. The troy ounce is the only remaining unit from the troy weighing system still in use.

Understanding the Troy Ounce

The troy ounce is the sole surviving unit from the troy weight system in modern practice. We use it to price metals like gold, platinum, and silver, so when you see metal prices per ounce, it's referring to the troy ounce.

It was also once used for certain gemstones, but the carat system has mostly replaced troy weights in the gem world.

History of the Troy Ounce

The troy system likely got its name from Troyes, France, a major trade center in the Middle Ages where merchants from Europe and Britain gathered. There, they defined a troy ounce as 480 grains of barley, with 12 troy ounces making a troy pound.

Some historians trace it back to Roman times, where bronze bars were divided into 12 'uncia' pieces, each about 31.1 grams.

As Europe's economy grew from the 10th century, a standardized weight system became essential for trade. Merchants in Troyes may have based theirs on Roman models.

King Henry II of England, born in France, aligned British coinage with the French troy system. Troy weights as we know them were first used in England in the 15th century.

Before that, Britain used the avoirdupois system for both precious and non-precious goods. By 1527, the troy ounce became the official standard for gold and silver in Britain, and the U.S. adopted it in 1828.

Troy Ounce vs. Ounce

The avoirdupois ounce, or just 'ounce' (oz), is what we use in the US for measuring foods and most items, except precious metals and gems. It equals 28.349 grams or 437.5 grains.

A troy ounce is heavier at 31.1 grams. The difference of 2.751 grams might seem small for tiny amounts, but it adds up for larger quantities.

When gold is priced at US$653 per ounce, that's a troy ounce. One standard pound has 16 standard ounces but equals 14.6 troy ounces. A troy pound, however, is 12 troy ounces and lighter, at 0.823 standard pounds.

Investing in Precious Metals

The distinction between troy and avoirdupois ounces mainly matters to precious metals investors.

Gold has long been a safe haven, though its price fluctuates due to its enduring nature. Today, it's joined by platinum and palladium.

Platinum, discovered by Europeans in South America in the 18th century, is a silvery-white metal used in jewelry, catalytic converters, and chemicals.

Palladium is scarce in nature, extracted from metals like platinum, copper, and zinc. It shares industrial uses with platinum and appears in medical, dental, and electronics equipment.

Ways to Invest in Precious Metals

You probably don't want to buy physical metals by the troy ounce and store them at home. Instead, consider these modern options:

Commodity ETFs or mutual funds let you invest easily—for instance, in a platinum ETF—without handling the metal; you just trade shares.

Shares in metals and mining companies offer direct exposure but come with risks tied to a single company's success in extraction.

Futures and options markets for precious metals are available online, though they're mostly for professionals and institutions.

Gold certificates, once government-backed, are now offered by banks and firms as a portable equivalent, backed by the issuer rather than a government.

Which Is Heavier: 1 oz. or 1 Troy Ounce?

A troy ounce is about 10% heavier than a standard ounce (1.0:1.097).

What Are Troy Ounces Used for Today?

We still use troy ounces for precious metals like gold and silver, and sometimes gemstones. Most other goods use the metric system or standard ounces.

What Is a Troy Pound?

A troy pound is 12 troy ounces, while a standard pound is 16 standard ounces. Thus, 1 troy pound equals 0.823 standard pounds.

The Bottom Line

Troy ounces measure gems and precious metals, equaling 1.097 standard ounces or about 10% more weight. The name comes from 16th-century Troyes, France, where it was standardized as 480 grains of barley. Note: Earlier versions of this info had errors in pound and kilogram conversions for troy ounces.