What is a Troy Ounce?

Posted on January 03, 2021

You may have noticed that some precious metals are measured using troy ounces. This standard unit of measurement is essential for all precious metals investors and collectors to understand.

What is a troy ounce?

A troy ounce is a unit of measure that is mainly used for the weighing of precious metals. One troy ounce is equal to 31.1034768 grams and is sometimes abbreviated using “t oz” or “oz t.” Even though the troy weighing system has been all but abandoned in other areas of commerce, it is still heavily used in precious metals for a standardized system of weighing.

Where did it originate?

scale for weighing troy ouncesThe system of troy measurements first began in England during the 1400s. It’s hypothesized that the name comes from the French town of Troyes, where English merchants came to trade with locals. The troy system was heavily influenced by the Roman monetary system, which was the world standard for centuries leading up until that point. The Roman system was combined with the previously used avoirdupois system of measurements utilized by the English at the time, which used pounds and ounces as units of measure (the same pounds and ounces used in America today -- a plain old everyday ounce is actually an avoirdupois ounce). Then, in 1527, England made the troy system the standard for gold and silver in the country.

It wasn’t long before the troy system became the standardized measurement system for gold and silver in the European region. And even though it was developed in England, the United States also adopted the troy weighing system as an official weight standard for coinage in 1828.

The troy weight system was followed by the English units standard of measurements for almost everything, except precious metals, which continue to be used in precious metals to this day.


Troy ounce compared to regular ounce



Troy Ounce

Regular Ounce

Weight (in grams)

31.1034768 grams

28.3495 grams


Troy oz, t oz (or, oz t)



Precious metals

Food, postal items, etc.

Size difference

9.7% larger

9.7% smaller


Troy pound vs. regular pound 

A troy pound is a unit of measure above the troy ounce in the troy weighing system. Unlike the traditional pound, which is divided into 16 ounces, the troy pound is divided into 12 troy ounces. Therefore, even though the troy ounce weighs more than the regular ounce, the troy pound (373.24 grams) weighs less than the regular pound (453.592 grams).

If you find this confusing, you’re certainly not alone. 

What about other troy measurements?

While the troy ounce is still commonly used in gold, silver, and other precious metals markets, the rest of the troy system has all but faded into obscurity. Other troy measurements like the pennyweight and grain are not commonly used today. In fact, even the previously used troy pound was eliminated by Britain in the 19th century and hasn’t been used since.

There are, however, a few exceptions in the U.S.:

  • Bullets and gunpowder charges are measured in grains
  • Arrows are weighed in grains
  • The hardness of water (dissolved calcium carbonate and equivalents) is often measured in grains per U.S. gallon 
  • Particulates in the air (typically pollutants) are measured in grains per cubic foot
  • The carat, still used for gemstones worldwide, is the equivalent of four grains 

Why do we still use the troy ounce for precious metal measurements?

Precious metals are a global market and therefore need an international standard of measure. Because the troy weighing system was used heavily throughout the years, it has become a go-to standard of measurement for bullion dealers worldwide. As such, it has been easy for precious metals traders to work in troy ounces as opposed to differing units of measure.
Consider, also, that if the troy ounce was replaced as the accepted unit of measure, an awful lot of bullion bars would need to be re-stamped or engraved with their weight in the new unit of measure. It would be an incredible hassle. Even though it might be harder for you and me to think in terms of troy ounces, it’s a whole lot easier than changing the precious metals industry’s conventions and traditions!
The troy ounce has lasted for hundreds of years, and as long as bullion continues to be a global market, it will likely continue to be used in the future.