Troy Ounce: Definition, History, and Conversion Table

Troy ounces are a unit of measurement used exclusively to weigh precious metals like gold, silver, platinum, and palladium. They’ve been used since the Middle Ages and remain the standard measurement in global precious metals trade today. If you’ve been exploring bullion products, you may have noticed the price of bars and coins quoted in ounces – this is nearly always referring to the troy ounce measure.  

Troy ounces are slightly heavier than the standard (avoirdupois) ounce used to weigh everyday items, such as grains or sugar. While a standard ounce contains 28.35 grams, the troy ounce weighs about 10% more at 31.10347 grams. This difference in weight might seem marginal, but it adds up to be significant – especially when dealing with large quantities. To properly understand the value and weight of precious metals, it’s essential for anyone interested in bullion to understand what troy ounces are and how they work. 

In this article, we dive into everything you need to know about troy ounces, including what they are, how much a troy ounce weighs, the history of troy ounces, and a conversion table to help you easily compare troy ounces with other units of measure. 

Key takeaways: 

• Troy ounces are the standard unit for weighing valuable metals like gold, silver, platinum, and palladium bullion products. 
• One troy ounce equals 31.1034768 grams. This is slightly heavier than the standard ounce, which weighs 28.349 grams. 
• The troy ounce is the last remaining metric of the troy weighing system that’s still in use today.
• It’s vital that anyone interested in precious metals understands the difference between troy ounces and regular ounces. Not doing so can lead to significant misunderstandings, especially when dealing with large quantities of metals. 

What is a troy ounce?

A troy ounce is a unit of measurement specifically used for weighing precious metals like gold, silver, platinum, and palladium. It is different to the common ounce (also known as the avoirdupois ounce) used for weighing everyday items. Troy ounces are commonly abbreviated to ‘t oz’ or ‘oz t’.  

Troy ounces have been used to measure metals for centuries. It’s said that they were first used in the city of Troyes in France, where a famous medieval fair became known for trading high-quality precious metals. The system was later adopted by the British in the Middle Ages and then by the United States. It’s now used worldwide in the trading of precious metals, and is the only remaining measure of the troy weighting system still in use today. 

Learning about troy ounces is essential for anyone interested in precious metals, as even a small difference in weight can have a significant impact on an item’s value. Whenever you see gold, silver, platinum, or palladium priced per ounce, it is almost always referring to the item’s troy ounce price. 

How much does a troy ounce weigh?

Troy ounces weigh about 10% more than standard ounces, with one troy ounce equating to 1.097 standard (avoirdupois) ounces.

In the metric system, one troy ounce is equivalent to 31.103476 grams.

While standard ounces are divided into 16 parts, troy ounces are divided into 20 parts, called pennyweights. Each pennyweight can be further divided into 24 grains. Each troy ounces contains a total of 480 grains, with each grain equating to 64.79891 milligrams. This meticulous precision is what makes troy ounces so suitable for valuing precious metals. 

When it comes to pounds, there are 14.6 troy ounces in an avoirdupois pound, compared to 16 standard ounces. There are troy pounds, too, which are slightly lighter than the standard pound. One troy pound contains 12 troy ounces. 

Sounds confusing? Don’t worry – all you need to understand when trading bullion is the troy ounce. 

History of troy ounces

The troy ounce’s history dates back to ancient times. While its exact origins aren’t quite known, it’s believed that troy weights originated in the French city of Troyes. This city was home to a bustling medieval trade hub where merchants gathered from across Europe. At some point, a weighing system emerged in Troyes, where 480 grains of barley equaled one troy ounce, and 12 troy ounces made up a troy pound. 

Some historians believe the troy ounce’s origins go back even further, as far as Roman times. The Romans were known for a monetary system that used bronze bars divided into twelve pieces. Each of these pieces was known as an ‘uncia’ or ounce, and weighed around 31.1 grams – a weight close to the modern troy ounce. It’s possible that the merchants in Troyes modeled their weight measurements on this Roman monetary system.  

When Europe’s economy began to expand during the 10th century, merchants from all across the world arrived to buy and sell goods. This made it necessary to develop a unified system that would simplify trade across all regions. Somehow, the French troy system gained traction and began to spread throughout the continent, reaching England in the Middle Ages. 

At the time, the British used an Anglo-Norman weighing system called the avoirdupois – or ‘goods of weight’ – system. King Henry II of England, a French-born monarch, decided to adjust the British coinage system to better reflect the French troy weight system. By 1527, the troy ounce had become the official measurement for gold and silver in Britain. 

The system eventually reached the United States, who formally adopted the troy ounce for coinage in 1828. It remains the global standard for weighing precious metals today. 

Troy ounce vs regular (avoirdupois) ounce

There are two main differences between a troy ounce and a regular (avoirdupois) ounce: troy ounces are slightly heavier than regular ounces and they’re used to measure precious metals as opposed to everyday items. Let’s go deeper into the two key differences between the two: 

• Weight: Standard ounces weigh 28.349 grams or 437.5 grains. On the other hand, troy ounces weigh 31.1 grams or 480 grains. 
• Uses: Standard ounces are used to weigh most goods while troy ounces are reserved for measuring precious metals. 

It might not seem like there’s a big difference in weight between troy ounces and standard ounces, but it becomes significant when you deal with larger quantities. So remember: whenever you see gold or silver prices quoted in ounces, it’s referring to troy ounces and not regular ounces. 

Why it’s important to know troy ounces

If you don’t know the difference between a troy ounce and a regular ounce, you could end up significantly miscalculating the value of gold or other precious metals. Let’s say gold is priced at $100 per ounce. If you assume this price applies to the standard ounce (28.35 grams) instead of the troy ounce (31.1035 grams), here’s what could go wrong: 

Let’s say you bought 10 ounces of gold. If you mistakenly believed that gold is priced by the standard ounce, you’d be expecting to buy 283.5 grams of gold (10 x 28.35 grams). But in the precious metals market, the $100 per ounce price is actually based on the troy ounce – meaning you should receive 311.035 grams (10 x 31.1035 grams). 

This misunderstanding could result in a difference of 27.535 grams, which is a lot!

Troy ounce conversion table

The table below converts troy ounces to other units of measurements. 

Troy ounce FAQs

Below, we answer some frequently asked questions about troy ounces. 

How much is a troy ounce in grams?

A troy ounce is equal to 31.103476 grams, compared to a standard ounce which weighs 28.349 grams.

Is a troy ounce heavier than a regular ounce?

Troy ounces weigh about 10% heavier than a regular ounce, with one troy ounce equalling 1.097 standard ounces.

What is an avoirdupois ounce?

An avoirdupois ounce is a standard ounce, equalling 28.349 gram or 437.5 grains

What is a pennyweight?

A pennyweight, abbreviated as ‘dwt’, is a unit of weight in the troy system. One pennyweight equals 24 grains and 20 pennyweights add up to one troy ounce. The unit’s symbol, ‘d’, traces back to the Roman denarius coin, which loosely equates to an English penny. Because the original troy pound was made from 12 troy ounces, there would have been 240 pennyweights in a troy pound – similar to the 240 pennies in the original pound sterling. 

What is a troy pound?

A troy pound is made up of 12 troy ounces, 5,760 grains, or 373.24172 grams. It’s slightly lighter than a standard avoirdupois ounce which contains 7,000 grains or 453.59237 grams. 

Why do people use troy ounces?

People use troy ounces to measure precious metals, like gold, silver, platinum, and palladium. This unit of measurement has a long history and is internationally accepted in the precious metals market, offering consistency and accuracy when weighing bullion and jewelry. 

Why is it called a troy ounce?

It’s believed that the term ‘troy ounce’ comes from the city of Troyes in France. This city was known for its popular medieval market, where people gathered from all over Europe to trade in goods. Here, the troy unit of measurement was developed to provide consistency.

What’s the difference between a standard ounce and a troy ounce?

The two main differences between a standard ounce and a troy ounce are their weights and uses. Troy ounces are slightly heavier than regular ounces, weighing 31.1035 grams as opposed to 28.3495 grams. Troy ounces are also reserved for weighing precious metals, while standard ounces are used to weigh nearly everything else. 

Why is it important to know troy ounces in precious metals?

It’s essential for anyone interested in precious metals to understand troy ounces as this is the standard unit of measure used to trade gold, silver, platinum, and palladium worldwide. To ensure consistency and accuracy across the globe, all precious metals are priced and measured in troy ounces. 

From an investment perspective, knowing troy ounces can help you understand the exact weight and value of the product you’re buying or selling. Since one troy ounce is about 10% heavier than a standard ounce, overlooking this difference could lead to costly misunderstandings – especially if you’re trading in large quantities. 

Are other troy weight units used in precious metals?

Yes, other troy weight units used in the precious metals industry include pennyweights and grains. These are often used when measuring smaller quantities of metals. There are 20 pennyweights and 480 grains in one troy ounce. 

Start investing in precious metals

Now that you’ve wrapped your head around the troy system, you’re ready to dive into the world of precious metals investments. 

The four main precious metals measured in troy ounces are gold, silver, platinum, and palladium. Each of these metals has their own unique properties and attributes, and all offer great opportunities for building and diversifying your wealth. 

You’re probably familiar with gold and silver, two timeless metals that have been used as a store of value for centuries. But let’s take a look at the two lesser-known precious metals, both of which hold great investment potential:

• Platinum: Platinum is a silvery-white metal that’s a relative newcomer to the precious metals market. Discovered in South Africa in the 1700s, platinum is extremely valuable in industries like automotive manufacturing, jewelry, and chemicals.
• Palladium: Palladium is a rare metal with unique properties that makes it essential in sectors like medicine, electronics, and dental tools. 

Summary: Troy ounces and precious metals investing

Troy ounces are the global standard when it comes to measuring precious metals like gold, silver, platinum, and palladium. This ounce is about 10% heavier than the standard avoirdupois ounce, coming in at 31.1035 grams compared to the standard 28.35 grams. 

If you’re buying, selling, or investing in precious metals, knowing what a troy ounce is and how it compares to other units of measure is essential for understanding the value and weight of the metals you’re dealing with. Misunderstandings can be costly – especially if you’re trading large quantities. By now, you should have a solid understanding of this weighing system and can navigate the precious metals market with confidence. 

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