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What is a Troy Ounce?

Troy Ounce vs. Ounce: Understanding the Difference in Precious Metal Measurements

September 01, 20232267 view(s)

The Troy ounce is far more than just a standard of weight. 


Originating in the medieval European trading town of Troyes, it serves as a critical cornerstone of the precious metals industry. Born out of the bustling trade fairs where a reliable and accepted standard of measure was indispensable, the journey of the Troy ounce is a fascinating tale that winds its way from the vibrant marketplace of Troyes, along European trade routes, and across the English Channel.


In this guide, we're going to help you understand the vital difference between Troy ounces and regular ounces. This knowledge is essential for anyone involved in the trading of precious metals, allowing you to communicate accurately and ensure fairness in your transactions.

Why Is it Called a Troy Ounce?

The term "Troy ounce" finds its roots in the medieval trading town of Troyes, France. But why specifically is it called a "Troy" ounce? The answer lies in the central role the town of Troyes played in European trade during the Middle Ages.


The city was a major site for trade fairs, which brought together merchants from all corners of Europe. With high-value items such as gold and silver changing hands, a reliable and universal system of measurement was critical for ensuring fair transactions. This necessity led to the birth and spread of the Troy weight system, a standard that took its name from the city where it gained prominence.


What's more, the influence of the Troy ounce extends far beyond Troyes and even the medieval era. The groundwork for this system was laid by ancient cultures such as the Greeks and Romans, who also used comparable units of weight.


As global exploration and colonization gained momentum, European nations like Britain carried the Troy system to their colonies, effectively globalizing its use. However, this adoption wasn't universal. Countries like China, for instance, adopted their own weight standard called the "tael" for precious metals.


Today, the Troy ounce remains a key unit in the precious metals industry worldwide despite regional variations. Its persistence is a testament to its historical significance and the continued need for a standardized system of measurement in global trade.



How Many Regular Ounces Are in a Troy Ounce?

Understanding the difference between a Troy ounce and a regular, or avoirdupois, ounce requires a quick trip back to your school math classes. Contrary to what might seem logical, a Troy ounce is not equivalent to a regular ounce. In fact, a Troy ounce is approximately 10% heavier.


A Troy ounce is defined as exactly 31.1034768 grams. On the other hand, an avoirdupois ounce, commonly used in the United States for everyday items, is lighter at 28.3495231 grams.


To make a comparison, if you have a weight of one Troy ounce, it would be equal to approximately 1.097 regular ounces. So, if you're dealing in precious metals and using Troy ounces, be aware that these are heavier than the ounces you might be familiar with from everyday life.


For those involved in buying, selling, or investing in precious metals, understanding the difference between a Troy ounce and a regular ounce is crucial. It comes down to a matter of value.


Given that a Troy ounce is heavier than a regular ounce, if you were to purchase gold, for example, on a price-per-ounce basis without specifying the type of ounce, you could find yourself at a loss. Buying one regular ounce of gold instead of one Troy ounce means you're getting about 10% less gold for your money.


This discrepancy can have significant financial implications, especially in large transactions or over time as investments accumulate. It could also affect your understanding of market prices and valuations when comparing investments or assessing market trends.


As all precious metals are internationally traded in Troy ounces, it's important to use the correct measurement to effectively participate in the global market. Each precious metal item is typically stamped with various markings, also known as hallmarks. These can include the manufacturer's mark, the fineness of the metal — also called its purity — and its weight.

For instance, a gold bar might be marked with "999.9", indicating that it is 99.99% pure gold. Additionally, it may have a marking such as "1 OZT," indicating that it weighs one Troy ounce. The "T" in "OZT" specifically refers to the Troy system. This is essential information for investors as it allows them to understand exactly what they're purchasing.

Understanding these markings can help investors ensure that they are buying a quality product, that they're getting what they're paying for, and that they can communicate effectively with sellers. It's also crucial when dealing with less common units of the Troy system, like Troy grains or pennyweights, as these may sometimes appear on historical or antique items. 


Being familiar with the Troy system units can help shield you from deceptive practices in the precious metals market. Some dealers might present items in lesser-known Troy units like grains or pennyweights or vaguely mark a bar as "1 OZ" rather than the correct "1 OZT." 


This can create an illusion of a better deal, leaving you with less precious metal than you expected. As an investor, it's essential to understand these markings and units, ensuring you get the value you're investing in. So, whether you're a seasoned investor, a hobbyist collector, or a beginner to precious metals, always remember: when it comes to precious metals, the weight that matters is the Troy ounce.


Is Gold Sold by the Ounce or Troy Ounce?


When it comes to buying and selling gold, the standard unit of measure is the Troy ounce, not the regular — or avoirdupois — ounce. This standard is used across the global precious metals market, which includes gold, silver, platinum, and palladium.


So, whether you're buying a gold bar in New York, a gold coin in London, or gold jewelry in Dubai, the weight of the gold will be calculated in Troy ounces. This consistency is important, as it allows for clear communication, accurate pricing, and fair transactions in the international gold market.

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