What is a troy ounce?

A troy ounce is used to weigh precious metals. Unlike a standard ounce, which weighs 28.35 grams, a troy ounce is equivalent to 31.103 grams. The troy ounce has been the industry standard for centuries, providing consistency in precious metals trading, investing, and valuation across the globe.

What is a troy ounce and how does it differ from an avoirdupois ounce?

A troy ounce is a unit of measurement used to weigh precious metals such as gold, silver, platinum, and palladium. It belongs to the troy weight system, which dates back to the Middle Ages where it was first used in Troyes, France. Today, the troy ounce remains the standard unit for pricing and trading in precious metals, ensuring consistent pricing, weight, and purity across global markets.

In contrast, the avoirdupois ounce is the standard unit of weight used in everyday commerce for items such as food, grains, and other commodities. This is the system most commonly used in the United States and United Kingdom for general weight measurements.

When precious metals prices are listed on charts or for sale per ounce, it is almost always referring to their weight in troy ounces. This is important to remember as, although the weight differences may seem minor, they can add up significantly when dealing with larger quantities of metals. Troy ounces are often abbreviated to ‘t oz’ or ‘oz t’.

Troy ounce vs avoirdupois ounce

The key differences between a troy ounce and an avoirdupois ounce are:

• The troy ounce is heavier: One troy ounce is equivalent to 31.1034786 grams, while a standard ounce weighs slightly less at 28.35 grams. This makes a troy ounce heavier than an avoirdupois once.
• The troy pound is lighter: One avoirdupois pound contains 16 ounces, while a troy pound consists of only 12 ounces. This means that a troy pound is actually lighter than a standard pound, even though a troy ounce is heavier than a standard ounce.

The table below outlines the differences between these two units of measure:

Why is the troy ounce the standard for precious metals?

The troy ounce is the standard weight for precious metals because it has historically been used in gold, silver, and platinum trading. Its adoption by the Royal Mint and the U.S. Mint helped establish the troy oz as the global measurement, providing consistency in precious metals pricing, weight, and purity.

Today, it is used by the London Bullion Market Association (LBMA), COMEX exchange, and other global markets to quote the prices of good delivery gold, silver, platinum, and palladium.

Troy ounce vs other units of weight

The troy ounce can be converted into various units of weight using the troy ounce conversion chart below.

The history and origins of the troy ounce in metal trading

The troy system for weights and measures has its origins in medieval Europe. The name is believed to come from the city of Troyes in France, a bustling trade hub during the Middle Ages where merchants from across Europe gathered for large-scale fairs trading wool, silk, fur, spices, and precious gold and silver wares.

To keep these fairs operating efficiently, the Counts of Champagne introduced rules governing weights – including the troy measurement system. In Troyes, 480 grains of barley were measured to equal one troy ounce, while 12 troy ounces made up one troy pound.

Some historians argue that the troy ounce dates back even further, with its roots in the Roman monetary system. Romans used standardized bronze bars that could be divided into 12 pieces called ‘uncia’ (the Latin word for ounce). Each piece weighed roughly 31.1 grams – the exact weight of a modern troy ounce. As trade expanded throughout Europe, medieval merchants may have modeled their weight system on this ancient Roman standard to create consistency in commerce.

By the 12th century, the troy system had spread across European markets, particularly in England under King Henry II. English coinage at the time was based on pennyweights, with 20 pennyweights equaling one troy ounce and 12 troy ounces forming one troy pound. This system ensured that silver and gold coins had a reliable weight standard for fair trade.

Despite the increasing use of the avoirdupois system (which measures 16 ounces per pound and is used for everyday goods), the troy system remained the standard for precious metals. By 1527, Britain officially adopted the troy ounce as its legal measurement for gold and silver, and the United States followed suit in 1828.

While many historical weight measures have come and gone, today the troy ounce is still used for pricing in the gold and silver markets.

What is 1 troy ounce of gold worth in global markets?

The value of one troy ounce of gold fluctuates based on global market conditions. Gold prices are influenced by several factors, including supply and demand, inflation, central bank policies, and geopolitical events. The price of gold is usually quoted in U.S. dollars per troy ounce.

Investors can track real-time gold prices through commodity exchanges or precious metals brokers.

Troy ounce vs avoirdupois ounce: implications for bulk metal purchases

Understanding the difference between a troy ounce and an avoirdupois ounce is essential for investors, refiners, and anyone dealing with precious metals. To reiterate, a troy ounce is heavier than a standard avoirdupois ounce, weighing 31.103 grams compared to 28.35 grams.

At first glance, the difference between a troy ounce and avoirdupois ounce may seem small, however it can have major implications when making bulk metal purchases. Misunderstanding these two units can lead to misvaluing assets, incorrect pricing, and significant financial losses. Investors should always ensure they’re purchasing precious metals bullion and commodities based on the correct weight system.

For example, if an investor mistakenly assumes that a gold bar weighing 100 standard ounces is equivalent to 100 troy ounces, they would be underestimating the metal's actual value. Since troy ounces are heavier, 100 standard ounces would only equal approximately 91.7 troy ounces, meaning the buyer would be receiving 8.3 fewer troy ounces of gold than expected. If gold’s price was $2,000 per troy ounce, this miscalculation could result in a loss of more than $16,000.

This example illustrates the importance of a standardized unit of measurement for precious metals. In almost all instances, the prices of precious metals bullion, gold commodities, and silver commodities will be quoted in troy ounces. However it never hurts to double check, particularly for large purchases.

Is the troy ounce used for all metals?

The troy ounce is exclusively used for weighing precious metals like gold, silver, platinum, and palladium. For most industrial metals – like copper, aluminum, and steel – the avoirdupois ounce remains the standard. This distinction matters when dealing with contracts and bulk shipments because weight discrepancies can impact transportation costs, hedging strategies, and contract fulfilment.

For example, a manufacturer purchasing 1,000 pounds of silver for industrial applications must ensure the weight is calculated in troy pounds and not avoirdupois pounds. Since a troy pound contains 12 troy ounces instead of the 16 ounces in an avoirdupois pound, the actual amount of silver being purchased would differ significantly if the incorrect system was used.

One simple misrepresentation of weight units in a contract could mean a buyer receiving significantly less metal than expected, which could increase costs and disrupt production schedules.

What are other units in the troy system?

Besides the troy ounce, other common units in the troy system include:

• Troy pound (lb t): Consists of 12 troy ounces or 373.24 grams. While once used to measure bulk quantities of metals, the troy pound is rarely used in the modern precious metals market.
• Pennyweight (dwt): Equals 1/20 of a troy ounce or 1.555 grams. Pennyweights are commonly used in jewelry manufacturing and scrap gold pricing.
• Grain (gr): The smallest unit in the troy system, with one troy ounce equaling 480 grains. Grains are still used today for measuring small amounts of gold, gunpowder, and some pharmaceuticals.

This material is for informational purposes only and should not be considered as an investment recommendation or a personal recommendation.