What Is a Troy Ounce?
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What Is a Troy Ounce?

By Joshua McMorrow-Hernandez
Published February 20, 2020
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A troy ounce is a unit of weight measurement developed in the Late Middle Ages. The troy weight system is still in use today for weighing precious metals.

The troy ounce as a standard unit of measurement is vital in the bullion world. Gold is measured in troy ounces. Even one tiny gram can mean a major difference.

Stack of Gold and Silver Bars

Virtually any gold coin or other precious metal coins use the troy system as their standard measurement.

When to Use the Troy Ounce Measurement

So, when you’re considering the purchase or sale of any precious metals, ensure that both you and the other party(ies) involved with the transaction are on the same page as to which type of ounce is being used to measure the goods!

You might laugh that such a mistake could occur with something so seemingly basic. But it does—and frequently, too.

1 ozt pirate silver bar

When dealing with any seasoned collector, investor, or dealer, assume the troy ounce is being referenced. This holds true for discussing anything numismatic in the context of "ounces."

This is especially the case when dealing with members of the non-numismatic public who might not be knowledgeable on the differences or conversions between troy ounces and avoirdupois ounces.

"Troy" Is French? Oui!

Where does the troy ounce get its name anyway?

The term derives from the French town of Troyes, located in the northern-central region of the nation. It serves as the capital of the French department of Aube in the administrative region known as Grand Est.

Troyes came to existence in the Roman era and evolved into an international trading hub during medieval times. It was during the Middle Ages (around the time of the Frenchborn King Henry II) that the city’s name inspired the unit of measurement now widely used in precious metals.

The city suffered a terrible fire in 1524. Yet the urban hub eventually recovered and is now the home of many museums, churches, and the production headquarters of popular French clothing company Lacoste.

How Much Is a Troy Ounce?

It's time to cover the basics. A troy ounce weighs 31.1035 grams, or 0.0686 pounds.

However, you're much more likely to find the grams conversion the more convenient of the two.

When dealing with large quantities of bullion, it’s probable you’ll be using kilos to express the weight, not pounds. We’ll cover kilos a bit later on in this article.

More important still is understanding how a troy ounce compares to an avoirdupois ounce. This is the "regular" ounce, as many might call it.

balance or scale used for weighing

As you may have already correctly surmised, there are differences between regular ounces and troy ounces.

In fact, there's a huge difference—especially if you're dealing in the precious metals market. The gold price (also known as spot price) is usually expressed per troy oz in the local currency.

The distinction affects the bulk sale of a product or actual size of a purchase. Thus, it's key to know the definition of what a troy ounce is when working with bullion material. This is true regardless of if you're a precious metals investor or coin collector.

While one troy ounce is equal to 31.1 grams, a regular ounce comes in at just 28.35 grams. That's nearly 3 grams less than the heavier troy ounce.

Put another way, an avoirdupois ounce weighs 2.75 grams less than a troy ounce, or nearly 9% less than a troy ounce. All told, there are 1.097142794 regular ounces in a troy ounce.

Also, there are 12 troy ounces in one troy pound, compared to 16 avoirdupois ounces in the more common regular pound.

How Many Grains In a Troy Ounce?

Grains, as you may know, is another commonly used term in the bullion world. It’s a metric system unit measuring mass, and there are 15.4323584 grains to a gram, or 64.79891 milligrams.

Meanwhile, 480 grains make a troy ounce.

By the way, while a grain is quite small, there are some bullion manufacturers who are making fractional bars and other products sold by the grain.

These products are miniscule in both size and weight. They are nevertheless affordable in the nominal sense. They help make gold, silver, and other bullion products offered in these tiny increments more widely available to a broader variety of buyers.

How Many Troy Ounces In a Kilo?

As you now know there’s a significant difference between a troy ounce and a regular ounce.

So, you may be wondering how troy ounces compare to other units of measurement. When it comes to precious metals, the most important of these other units of measure is the kilogram (kg).

gold kilobar

Example of a gold kilobar

A kilo is a unit of measurement based in direct conversion and in name upon the gram. There are 1,000 grams to a kilo.

What does that equate to in troy ounces? A kilo is 32.1507 troy ounces.

Once more, a kilo is 1,000 grams—not 1,000 troy ounces!


Joshua McMorrow-Hernandez is a journalist, editor, and blogger who has won multiple awards from the Numismatic Literary Guild. He has also authored numerous books, including works profiling the history of the United States Mint and United States coinage.

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