What Is the Difference Between a Troy Ounce & an Ounce?

Synopsis

Gain a comprehensive understanding of the distinctions between troy ounces and ounces of precious metals, including historical context, weight variations and conversion factors, and the implications on value and purity. Indispensable knowledge for discerning investors, traders, and collectors.

The Importance of Knowing the Difference

When discussing the realm of precious metals, it is crucial to distinguish between the terms "troy ounce" and "ounce." Although they may seem interchangeable, they possess distinct historical origins and have different uses for the purpose of measurement of weight. All too often, we have seen many people, including the Police and media get the distinction wrong in news reports, which perhaps highlights, just how easy it is to get confused!  They should have double checked the differences with Chards! 

Fun Facts

An ounce of gold is heaver than an ounce of lead.

There are 12 Troy ounces in a Troy Pound.

A pound of lead is heavier than a pound of gold.

One troy ounce is 31.1034768 grams

One avoirdupois ounce is 28.349523125 grams

Don't try and bake a cake, using Troy Ounce measurements. You may be seriously disappointed with the results! 

What is an Ounce?

An ounce is a unit of measurement that is used to measure a variety of different things, including weight, volume, and mass. It is also know as an avoirdupois ounce. It is defined exactly as, 28.349523125 grams and is equal to 1/16 of an avoirdupois pound. Sixteen ounces make up one avoirdupois pound. Ounces are used to measure a variety of items, including food, and liquids. The term "avoirdupois" has its roots in the Anglo-Norman phrase "avoir de pois," meaning "goods of weight," reflecting its historical use in weighing general merchandise. 

What is A Troy Ounce?

A troy ounce is a unit of weight that is commonly used to measure the weight of precious metals, such as gold and silver, ensuring consistency across the industry. A troy ounce is heavier than a regular avoirdupois ounce and is based on a traditional system of weights and measures. It is the standard unit of measurement for gold, silver, and other precious metals. It is slightly heavier than a standard ounce, with one troy ounce equaling approximately 31.1 grams (31.1034768 grams).

The Measurement for Precious Metals

The troy ounce, is believed to have originated in the medieval European city of Troyes. It was a significant trading centre during that time, and the weights used there, known as the "Troy system," became the standard for measuring precious metals. Over time, the Troy ounce was adopted by various regions and eventually became the standard for gold and silver.

Weight and Conversion Factors

It is important to note that the troy ounce is slightly weightier than the standard ounce, at 31.1034768 grams, or 1.097142857 troy ounces, compared to 28.349523125 grams, or 1 ounce. This slight discrepancy can prove significant when dealing with large quantities of precious metals, as it can translate to a difference in value. Additionally, it is necessary to be familiar with the conversion factor, as one troy ounce is equivalent to 1.097142857 ounces, and one ounce is equivalent to 0.911458333 troy ounces.

Purity of Precious Metals

Furthermore, the difference in weight between the two measurements also affects the purity of precious metals. A gold bar marked as "999.9 pure," for example, would actually be 99.99% pure gold when measured in troy ounces, but only 99.99% pure gold when measured in ounces.

Buying and Selling Precious Metals in the United Kingdom

It is crucial to understand that the troy ounce is primarily used in the precious metal industry, specifically in the buying and selling of gold and silver. The price of these metals is commonly quoted in troy ounces and most precious metal products such as gold coins and bars are also measured in troy ounces. On the other hand, the standard ounce is mainly employed in everyday measurements such as weight and volume. This is particularly important to keep in mind when purchasing or selling precious metals in the United Kingdom, as the price is typically quoted in troy ounces.

Difference Between Troy Ounce & Ounce for Precious Metals

In conclusion, it is imperative for those involved in the world of precious metals to be cognizant of the differences between a troy ounce and an ounce. The troy ounce is primarily used in the precious metal industry while the standard ounce is mainly employed in everyday measurements. Furthermore, the difference in weight and conversion factor can have a significant impact on the value and purity of precious metals. It is important for investors and sellers to use the correct measurement and be aware of the conversion factor when buying or selling precious metals to ensure accurate calculations. This knowledge is essential for anyone involved in the high-end precious metal market, whether as an investor, trader, or collector. Understanding the difference between a troy ounce and an ounce can help to prevent confusion and ensure that transactions are conducted with precision and accuracy. It is essential for anyone dealing with precious metals to be aware of these distinctions and to use the appropriate measurements for the task at hand.

Author: Lawrence Chard - Chairman and CEO

Published: 19 Jan 2023

Last Updated: 17 Jul 2025

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