What is a troy ounce?

The troy ounce is an international unit of weight used to measure precious metals. Although its name is sometimes mistakenly associated with ancient Troy, it actually comes from the medieval city of Troyes in France, one of the most important trading centers of that era.

The troy ounce remains the global standard for trading gold, silver, and other investment metals to this day. Below, we explain its origin, exact weight, and key differences from other units of measurement.

Table of contents

• What is the history and origin of the troy ounce?
• How much does a troy ounce weigh, and what is it used for?
• How does a troy ounce differ from other units of weight?

What is the history and origin of the troy ounce?

The troy ounce originates from the medieval weight system used in the city of Troyes, which was an important trading center in Western Europe in the 12th and 13th centuries. The local weight standard, valued for its precision and repeatability, quickly gained popularity in international trade.

This system was then adapted in England, where it was used in coinage, and over time became the basis for the valuation of precious metals in Anglo-Saxon countries. In the following centuries, the troy ounce was also adopted in the United States, consolidating its position as a universal unit of weight for the precious metals market.

How much does a troy ounce weigh, and what is it used for?

A troy ounce has a strictly defined weight of 31.1034768 grams, which in commercial practice is rounded to 31.1 grams. This unit forms the basis for the valuation of precious metals on global markets and is used to determine the weight of:

• gold,
• silver,
• platinum,
• palladium.

It is in troy ounces that the weight of bullion coins, investment bars, and metal prices quoted on exchanges are given. For the sake of clarity, it is worth adding that one troy ounce is equal to 480 grains (i.e., approx. 31.1 g), and one kilogram contains approx. 32.15 troy ounces.

How does a troy ounce differ from other units of weight?

The main difference between a troy ounce and other weight units is its mass. A troy ounce is significantly heavier than the commonly used international ounce (avoirdupois), which weighs 28.35 grams.

Differences also exist at the level of larger units. A troy pound consists of twelve ounces, while in the avoirdupois system, a pound consists of sixteen ounces. This discrepancy makes the two systems incompatible with each other.

For this reason, precise differentiation between units is crucial in trade and investment. Using the wrong weight system can lead to significant errors in valuation and accounting, especially in the case of precious metals.