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What Is a Troy Ounce?


Written by John Rothans

Jun 24, 2022

Troy Ounce Defined

A troy ounce is a unique weight used for precious metals and gems. It is based on a 12-ounce pound instead of a traditional 16-ounce pound, which means that a troy ounce actually weighs more than a standard (or imperial) ounce. How many grams are in a troy ounce? A troy ounce is 31.1034768 grams, or 0.0311034768 kilograms.

History of the Troy Ounce

The term “troy ounce” is believed to come from a unit of measurement first used in Troyes, France, in the Middle Ages, created for use by traveling merchants as a standard measurement of exchange. The troy measurement system includes the grain, the pennyweight, the troy ounce, and the troy pound. During the 15th and 16th centuries, France and England made the troy ounce their standard for measuring gold and silver. In 1828, the United States followed suit. The troy ounce is now the international standard in most countries for measuring gold, precious metals, and gems.

The imperial ounce, also known as the avoirdupois ounce, is based on a 16-ounce pound. During the 14th century, England started using the avoirdupois ounce as a basis for measuring grain and textiles. When America was first colonized by England, the colonies carried over the imperial/avoirdupois system of measurement. In 1824, the United Kingdom adopted legislation that shifted the standard of weights and measurement from the imperial system of ounces to the stone system, with one stone (st) equal to 14 imperial pounds.

While today countries around the world use a variety of weight measuring systems—most use the metric system, though the United Kingdom and Ireland still often use the stone system for measuring body weight, and the United States uses the imperial/avoirdupois system for measuring most weights—the troy ounce is used by all of these nations for weighing gold, precious metals, and gems.

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

How Many Troy Ounces Are in a U.S. Ounce?

One troy ounce is equal to about 1.097 U.S. ounces. Interestingly, while a troy ounce is heavier than a U.S. pound, a troy pound is actually lighter. A troy pound is equal to 5,760 grains, whereas an avoirdupois pound, the standard measurement in the United States for dry course goods, is equal to 7,000 grains.

When Are Troy Ounces Used?

Most countries in the world use grams and kilograms as their standard weights of measurement. The avoirdupois system is still used only in the United States. Here it is not only the standard of measurement for things like flour, textiles, and other dry goods, but is also used as the basic unit of measurement for all weights, with the exception of gold, precious metals, and gems.

The troy ounce is used exclusively as a standard measurement for gold, silver, and other precious metals around the world, and it is the only unit within its measurement system still commonly used today—a detail that sets it apart from other modern measurement systems.

Is a Troy Ounce Heavier or Lighter Than an Ounce?

A troy ounce is heavier than a standard U.S. (avoirdupois) ounce. A troy ounce is about 1.097 ounces avoirdupois, or roughly 9.7% heavier.

How Much Is a Troy Ounce of Gold Worth?

When it comes to weight, a troy ounce doesn’t change over time. However, the price of gold does fluctuate, which means there is no set price for a troy ounce of gold. Depending on various market factors and/or conditions, one troy ounce of gold may cost more or less on any given day. For example, the price of one troy ounce of gold in 1923 was about $20. In August 2020, gold reached an all-time high of $2,072.49 for one troy ounce of gold. Note: This spot gold price is still written as $2,072.49/oz., as both imperial and troy ounces use the same abbreviation. However, in the gold bullion market it is understood that any mention of an ounce is referring to a troy ounce.

This tendency to fluctuate in price is true for all precious metals. For example, the price of a troy ounce of silver in 1923 was around $11. In April 2011, a troy ounce of silver traded at a record high of $47.34.

You can explore current and historic prices of gold and other precious metals on our website.

Why Are Troy Ounces Important?

Gold and other precious metals are traded internationally. The precious metals industry has multiple sectors, including discovery, production, and trade. In order to maintain consistency across all sectors, as well as international borders, a standard measurement of weight for gold and other precious metals is essential.

Part of this consistency relates to the historical prices of gold and other precious metals. Since the troy ounce was used historically, continuing its use helps the industry maintain a sense of continuity and helps with long-term price tracking.

If you are purchasing gold, gems, or other precious metals, it is important to remember that they are measured in troy ounces. While the shared abbreviation “oz.” is often used, the spot price of each of these is listed in troy ounces, not imperial ounces. If you receive gold, silver, or palladium and measure its weight at home, you will need to use a troy ounce scale. If you use a normal scale with imperial ounces, the measurement will not align with current international standards.

Buying gold at “spot price” means buying it at its current market price. The price of gold, silver, and palladium all fluctuate throughout the day, so the spot price at any given minute may be different than the average price listed at the end of each day. For help buying gold at the spot price, visit our article.

Understanding your Next Precious Metals Purchase

Understanding what a troy ounce is and why it is used by the gold and precious metals industry will help eliminate confusion as you look to enter the world of physical precious metals ownership. In short, a troy ounce is a unit of measurement separate from, and slightly heavier than, a regular ounce, also known as an imperial or avoirdupois ounce. When you see the market or “spot” price of gold, gems, or other precious metals, that price is listed in dollars per troy ounce.

If you are interested in purchasing gold or other precious metals or want to learn more about gold, request a free information kit here.


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