A troy ounce is a unit of measurement that’s predominantly used for precious metals such as gold, silver and platinum. The troy ounce is different from the avoirdupois ounce, which is used to measure the weight of food and other items in the United States.
Key highlights:
The troy ounce is equivalent to 31.103 grams.
The avoirdupois ounce (more commonly referred to simply as the “ounce”) is equivalent to 28.349 grams.
The troy ounce can be abbreviated to “t oz”, “oz t”, or “ozt”.
The troy ounce is a part of the troy weighting system, which is most likely named after the French market town of Troyes. Even though it’s likely named after a French town, the troy system as we know it today started being used in the 15th-century Kingdom of England.
The troy weighting system consists of the troy pound, the troy ounce, the pennyweight and the troy grain.
Unit Equivalent to In grams Troy pound 12 troy ounces 373.241 Troy ounce 20 pennyweights 31.103 Pennyweight 24 grains 1.555 Grain n/a 0.064
However, the troy ounce is the only unit of measurement from the troy system which is still in active use.
Troy ounce vs. ounce
The standard unit of measurement for food and other items in the United States is the avoirdupois ounce, which is usually referred to as “ounce”. The ounce is equivalent to 28.349 grams and is often abbreviated to “oz”.
Meanwhile, the troy ounce is used to measure the weight of gold, other precious metals and gems. The troy ounce is equivalent to 31.103 grams and is abbreviated to “t oz” or “oz t”.
If you see the price of precious metals such as gold expressed in dollars per ounce, there’s a very high likelihood that the price is referring to the troy ounce and not the ounce.
One interesting fact about the avoirdupois system and the troy system is that even though the avoirdupois ounce is lighter than the troy ounce, the avoirdupois pound is heavier than the troy pound.
The avoirdupois pound is equivalent to 16 avoirdupois ounces, which works out to 453.5 grams. The troy pound is equivalent to 12 troy ounces, which works out to just over 373 grams.
Converting a troy ounce into other units of measurement
Now, let’s take a quick look at how to convert a troy ounce into other common units of measurement:
1 troy ounce is equivalent to:
1.097 ounces
0.0685 pounds
31.103 grams
0.0311 kilograms
155.517 carats
Be mindful of troy ounce vs. ounce when purchasing precious metals
When purchasing a one-ounce gold coin and comparing it to a standard ounce, you’ll notice it weighs 10% more. This is because the two measurements are different and should not be compared directly. While the troy ounce system may initially seem more complex, it’s essential for maintaining purity standards in precious metals.
Recognizing the difference between a troy ounce and a regular ounce allows you to buy confidently from trustworthy precious metals dealers. It's always wise to ensure that the dealer specifies the weight in troy ounces or its equivalent in grams, rather than just using ounces.
FAQs
Let’s answer some of the most common questions users have when it comes to the difference between a troy ounce and an ounce.
How many grams are in a troy ounce?
There are 31.103 grams in 1 troy ounce. The troy ounce is heavier than the standard (avoirdupois) ounce, which is equivalent to 28.349 grams.
Troy oz vs. oz – What’s the difference?
The difference between the troy ounce and the ounce is that the troy ounce is primarily used to measure precious metals and gems, while the ounce is used to measure food and other items commonly encountered in our daily lives. The troy ounce (31.103 grams) is heavier than the ounce (28.349 grams).
The troy ounce is the standard unit of measure when discussing the price of precious metals.
If you see the weight of gold or other precious metals specified in “oz”, the seller could still be referring to troy ounces even though they might not explicitly write it as “t oz” or “oz t”. Before making any purchases, make sure to double-check whether the seller is referring to troy ounces or ounces.
The price of gold in ounces typically refers to troy ounces and not ounces.
What’s the weight of a gold bar in troy ounces?
Central banks and bullion dealers typically hold and trade gold bars that weigh roughly 400 troy ounces (12.4 kilograms).
Another very common type of gold bar is the 1 kilogram gold bar, which is equivalent to roughly 32.15 troy ounces.
If you want to learn more about gold bars, we recommend you check out our article exploring the price of gold bars and other interesting facts about them.
The bottom line
It’s important to understand the difference between the troy ounce and the ounce, especially if you’re someone who is interested in investing in precious metals. The troy ounce is the default unit of measuring weight in the precious metals industry.
Although the troy ounce is less than 10% heavier than the ounce, the difference can add up to huge numbers if we’re talking about substantial amounts of gold or other precious metals. So, it’s always important to know whether someone who’s buying or selling gold is referring to troy ounces or ounces.
If you’re looking to invest in gold but don’t want to deal with the hassle of storing physical gold, you should consider alternative ways of investing in gold. For example, gold-backed crypto tokens are fully backed by gold and you can store them in your crypto wallet, just like any other token.