What is a troy ounce? Why is gold and silver measured in troy ounces? Are they different from a standard or avoirdupois ounce?
You’ll be an expert on the weights of precious metals by the end of this article…
Table of Contents
- What is a Troy Ounce?
- How Many Grams in a Troy Ounce?
- Troy Ounce vs Standard Ounce (Avoirdupois Ounce)
- Why is it a Troy Ounce? History of the Troy Ounce
- Does the Troy Ounce Change the Precious Metals Price?
- Buying and Selling Precious Metals in Troy Ounces
What is a Troy Ounce?
The troy ounce is the unit of measure used for precious metals such as gold, silver and platinum. Somewhat confusingly the troy ounce is not a part of the metric system or the old imperial system of measurement that is still used in the USA. Also confusing is that base metals such as copper are not measured in troy ounces but in standard or avoirdupois ounces.
How Many Grams in a Troy Ounce?
A troy ounce is equal to 31.1034768 grams (which is in turn equal to 480 grains), or 0.0311034768 kilograms.
While a kilogram contains 32.15 troy ounces.
The fact that these 2 conversion factors (31.10 and 32.15) are quite similar can lead people to use one instead of the other and arrive at incorrect numbers when converting kilograms prices to troy ounces.
So make sure you use the right number!
What is the Abbreviation for a Troy Ounce?
The abbreviation for a troy ounce is: oz t. However in the gold and silver community the troy ounce is such an accepted and universal measure that you’ll generally just see it abbreviated as: oz.
Troy Ounce vs Standard Ounce (Avoirdupois Ounce)
A troy ounce is approximately 10% heavier than the standard or avoirdupois ounce that is commonly used in America to measure food. Conversely you can convert a standard ounce into a troy ounce by dividing the standard ounce by 0.91.
If you want some further confusion then also know that there are only 12 Troy ounces to a troy pound. Whereas a standard pound contains 16 ounces. So a troy ounce is heavier than a standard ounce, but a troy pound is lighter than a standard pound!
But fear not! As the troy pound is not used at all in quantifying modern precious metals. Instead you’ll see only, gram, troy ounces, and kilograms.
Interesting Side Fact About Troy and Avoirdupois Ounces:
The troy and avoirdupois systems share the same basic legal unit: the grain. This harks all the way back to the Bronze Age, when the measurement of mass was based on a single seed of a cereal plant such as wheat or barley. Variations in weight between plant species and even same species created obvious discrepancies. Finally, the issue became subject to modern formalization in 1959 under the International Yard and Pound Agreement, and that is the foundation of our weight system: 7,000 grains make up one avoirdupois (American) pound. But … there are only 5,760 grains in a troy pound.
…gun experts may recognize [the grain] as the unit of measurement for the mass of bullets and propellants, reflecting the value placed on ammunition in world history, on par with that of gold and silver wealth. A single particle of gunpowder is also known as a grain. Furthermore, although rarely ever used anymore, weights in the apothecaries’ system are equivalent to those of the troy system: a standard aspirin tablet contains 5 grains.Source.
Why is it a Troy Ounce? History of the Troy Ounce
So why do we use troy ounces?
Despite the horse in our featured image on this page, a troy ounce has nothing to do with the ancient city of troy.
The troy ounce is likely a carry over from the Roman system for measuring gold and silver in order to preserve the standards previously set across time, as the two-system standard would have created problems for the monetary system of the day.
Troy ounces have been used in England since about 1400 and the English troy ounce was officially adopted for coinage in 1527. The troy ounce in use today is essentially the same as the British Imperial troy ounce (1824–1971), adopted as an official weight standard for United States coinage by Act of Congress on May 19, 1828.Source.
Some historians believe the troy ounce obtained its origins from Roman times. Romans standardized their monitory [sic] system using bronze bars that could be broken down into 12 pieces called “uncia” or ounce, with each piece weighing around 31.1 grams. As Europe’s economic importance grew from the 10th century onward, merchants came from all over the world to buy and sell goods there. It was therefore necessary to develop a new standardized monetary weight system to make doing business much easier. Some believe the merchants of Troyes [a french market town] modeled this new monetary system using the same weights as their Roman ancestors.Source.
Does the Troy Ounce Change the Precious Metals Price?
Someone new to the world of precious metals may wonder whether the troy ounce somehow changes the price you see quoted for precious metals.
However the price in troy ounces is what all other weights of gold and silver are based upon. So if you see prices for grams or kilograms of gold or silver, these are simply conversions based upon the current per troy ounce prices.
Buying and Selling Precious Metals in Troy Ounces
Troy ounces are the standard unit of measure for gold and silver across the planet. So make sure you are buying gold or silver in troy ounces and you really can’t go wrong.
All gold coins and silver coins from various sovereign mints are always produced in troy ounce sizes.
Likewise all gold and silver products we sell here at Gold Survival Guide are all priced in troy ounce sizes. Whether they be coins or bars. Silver is commonly priced in kilograms but as stated earlier, this per kg price is converted from the troy ounce price too.
Next you might also want to see: What Does Gold Spot Price (Or Silver Spot Price) Mean?
Editors Note: This article was originally published 8 May 2018. Last updated 20 October 2020.