# Understanding the Troy Ounce: History, Definition, and Precious Metals

![Troy Ounce: A unit of measure used for weighing precious metals.](https://www.investopedia.com/thmb/RuayVgScil-GR9Ovl8xaH-sLFJI=/1500x0/filters:no_upscale():max_bytes(150000):strip_icc()/troyounce.aspfinal-4a6c671e8ba84faab23d5012beae5091.jpg)

*— Investopedia / Candra Huff*

> **Definition**
>
> A troy ounce is a system of measurement used to weigh precious metals and gems.

## What Is a Troy Ounce?

A troy ounce is part of the troy system of weights and measures, and the only unit of that system still in use. The troy ounce is used when weighing [precious metals](https://www.investopedia.com/terms/p/preciousmetal.asp). The name is thought to derive from the town of Troyes in Frances, which in the Middle Ages was a trading hub for Europe and Britain. One troy ounce is equal to 31.1034768 grams, according to the UK Royal Mint. A standard ounce is lighter than a troy ounce, weighing in at 28.35 grams.

### Key Takeaways

*   The troy ounce, a unit of measurement used mainly for precious metals, dates back to the Middle Ages and the French city of Troyes; it evolved from earlier Roman systems.
*   A troy ounce is 31.1034768 grams, making it approximately 10% heavier than a standard ounce, which is 28.349 grams.
*   The troy ounce remains the standard for pricing and trading precious metals like gold, silver, and platinum in the global market, ensuring consistency in weight and value.
*   While the troy ounce is still used for precious metals, most other goods are measured using the metric system or the avoirdupois ounce.
*   The troy weight system is largely historical, with the troy ounce being the only measure still commonly used today, underscoring its enduring significance in the metals market.

## Modern Uses and Significance of the Troy Ounce

The troy ounce is the only part of the troy weight system still used today. It's used to price metals like gold, [platinum](https://www.investopedia.com/terms/p/platinum.asp), and silver. So, when metal prices are listed per ounce, the reference is to the troy ounce.

It was also used when weighing certain gemstones. The troy weight system, however, has largely been replaced by the [carat](https://www.investopedia.com/terms/f/fourc.asp) system in the world of precious gems and stones.

## Historical Evolution of the Troy Ounce

The troy system for weights and measures is believed to have gotten its name from the French city of Troyes, a business hub in the Middle Ages that attracted merchants from around Europe and Britain. In Troyes, merchants measured 480 grains of barley to equal a troy ounce, and 12 troy ounces equaled one troy pound. 

Some historians think the troy ounce started in Roman times. Romans used bronze bars for money, divided into 12 pieces called "uncia" or ounces, each weighing about 31.1 grams.

From the 10th century, as Europe's economy grew, merchants worldwide traded there. A new standard weight system was needed for easier business. Some think Troyes' merchants based their system on Roman weights.

Before the adoption of the metric system across Europe, the French-born King Henry II of England adjusted the British coinage system to better reflect the French troy system. The system was adjusted periodically, but troy weights, as we know them today, were first used in England in the 15th century.

Before the troy system, Britain used the Anglo-Norman French avoirdupois system, meaning "goods of weight," for weighing all metals. By 1527, Britain had adopted the troy ounce for gold and silver, and the U.S. did so in 1828.

## Comparing Troy Ounces to Standard Ounces

The avoirdupois ounce, simply referred to as ounce (oz), is the standard used in the US to measure foods and other items, with the exception of precious metals and gems. It is the equivalent of 28.349 grams or 437.5 grains. A troy ounce is a little heavier, with a gram equivalent of 31.1. The difference (2.751) may be minute for a small quantity, but can be substantial for large quantities.

When gold is priced at $653 per ounce, it’s a troy ounce. A troy ounce is heavier than a standard ounce, with 14.6 troy ounces in a pound, compared to 16 standard ounces. Don’t confuse this pound with a troy pound, which is lighter at 12 troy ounces.

## Easy Conversion Guide for Troy Ounces

Below is a quick reference table for converting troy ounces into other common weights.

## Investment Insights for Precious Metals

The difference between a troy ounce and an avoirdupois ounce is of concern mostly to investors in precious metals.

Gold has historically been seen as the ultimate safe haven, although its market price is volatile, not least because of its status as an imperishable asset. But the age-old practice of using gold and silver as a store of wealth has been joined in modern times by two more precious metals:

*   Platinum is a relative newcomer to international precious metals trading, having been "discovered" by Europeans in South America in the first half of the eighteenth century. This silvery-white metal is used in high-end jewelry, but its main use is in catalytic converters for vehicles. It also has uses in the chemical industry.
*   Palladium is rarely found in nature but can be extracted for commercial use from other metals, including platinum, copper, and zinc. It has the same industrial uses as platinum and is also used in medical, dental, and electronics equipment.

### Ways to Invest in Precious Metals

Most modern investors probably don't want to buy precious metals by the troy ounce and stow them in a safe at home. Luckily, there are modern ways to invest in these metals:

*   Commodity exchange-traded funds (ETFs) or mutual funds are an easy way to get into investing in precious metals. For example, you decide to invest in one [platinum ETF](https://www.investopedia.com/platinum-etfs-how-they-work-8426153). Just as with any fund, you don't take delivery of the metals you own through the fund, but you can buy and sell fund shares all the same.
*   Common stock shares of companies in the [metals and mining sector](https://www.investopedia.com/ask/answers/040615/what-metals-and-mining-sector.asp) are a more direct way to gain a stake in precious metals. They're riskier, too. You're putting your money on a single company's luck at locating and extracting the precious stuff.
*   Futures and [options markets](https://www.investopedia.com/options-basics-tutorial-4583012#:~:text=Options%20are%20contracts%20that%20give,purchased%20with%20brokerage%20investment%20accounts.) exist for precious metals. Internet access has made all things accessible but these markets are dominated by professional traders and institutional investors.
*   [Gold certificates](https://www.investopedia.com/terms/g/goldcertificate.asp), once a usable form of government-issued currency, can still be purchased from some banks and investment companies. They are basically a portable gold equivalent, but they're no longer backed by the full faith and credit of any government. They're backed by the entity they are purchased from, with the potential risk that implies.

## Which Is Heavier: 1 oz. or 1 Troy Ounce?

A troy ounce is approximately 10% heavier than a standard ounce (1.0:1.097).

## What Are Troy Ounces Used for Today?

Troy ounces are still used in measurements of precious metals (like gold and silver) and gemstones. Most other goods are weighed using either the metric system or standard ounces.

## What Is a Troy Pound?

A troy pound is 12 troy ounces (while a standard pound is 16 standard ounces). 1 troy pound = 0.823 pounds.

## The Bottom Line

The troy ounce is the unit of weight used for precious metals like gold, silver, and platinum. It continues to play an important role in ensuring market consistency and purity standards. It is the only part of the troy system of weights and measurement that's been in continuous use since the Middle Ages to the present day. The troy system is believed to have originated in the trade center of Troyes, France, which standardized the troy ounce at 480 grains of barley. Today, one troy ounce converts to 31.10 grams. A standard ounce equals 28.35 grams.  

**_Correction—Nov. 5, 2022:_** A previous version of this article misstated the conversion amounts for a pound and a kilogram, as it relates to the troy ounce.

> **Article Sources**
>
> 1.  The Royal Mint. "[What Is a Troy Ounce?](https://www.royalmint.com/faqs/bullion/what-is-a-troy-ounce/)"
>     
> 2.  Karat Gold. "Weights and measures." Maguire Reference, 1982.
>     
> 3.  JM Bullion. "[What Is a Troy Ounce?](https://www.jmbullion.com/investing-guide/types-physical-metals/troy-oz/)"
>     
> 4.  International Society of Weighing and Measurement. "[Weights and Measures Tables](https://www.iswm.org/weights-and-measures-tables)."
>     
> 5.  Royal Society of Chemistry. "[Platinum](https://www.rsc.org/periodic-table/element/78/platinum#:~:text=Platinum%20is%20used%20extensively%20for,into%20less%20harmful%20waste%20products.)."
>     
> 6.  Society of Chemistry. "[Platinum](https://www.rsc.org/periodic-table/element/78/platinum#:~:text=Platinum%20is%20used%20extensively%20for,into%20less%20harmful%20waste%20products.)."