What is the difference between troy ounce and regular ounce

What is a Troy Ounce?

First-time precious metals buyers are often confused by the difference between a troy ounce (ozt) and a “regular” ounce, especially when their 100 oz silver bar actually weighs 6.85 lbs on the scale instead of 6.25 lbs. Did they receive more silver than they paid for? The answer lies in an antiquated system of measurement still used today for precious metals known as troy weights.

But first: what exactly is a “regular” ounce? We remember from grade-school that an ounce is 1/16 of a pound, and when we visit the grocery store and ask for half-a-pound of cheese, we expect to receive eight ounces in return. This extremely common unit of measure is known as an avoirdupois ounce, and it is used for measurements not involving gold, silver, platinum, or gunpowder.

The troy ounce was retained from the Roman system for these four commodities 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.

A troy ounce is 1/12 of a troy pound (a troy pound is actually lighter than an avoirdupois pound). The troy ounce (480 grains) is heavier than the avoirdupois ounce (437.5 grains). A grain is 64.79891 milligrams (mg); therefore one troy ounce is 31.1034768 grams (g). This measures out to be about 10 percent more than the avoirdupois ounce, which is 28.349523125 g.

1 troy ounce = 1.09714286 ounces (avoirdupois)

Troy ounce to metric metric measurements

As mentioned above, one troy ounce is equal to 31.1034768 grams. Therefore, one kilogram is equal to 32.1507 troy ounces.

• August 16, 2018
• By Gold Price

Investors use troy ounces to weigh precious metals. A troy ounce equals 1.09714 ounces and 0.0685714 pounds.

thad/iStock via Getty Images

What Is a Troy Ounce?

A troy ounce is a measurement used for weighing precious metals like gold, silver, platinum, and palladium. While there are disagreements as to its origin, the most commonly held belief is it originated in Troyes, France during the Middle Ages.

One troy ounce is equal to 31.1034768 grams, and 12 troy ounces make up one troy pound. Instead of oz, which represents the avoirdupois ounces, the abbreviation for a troy ounce is ozt. In the commodities market, precious metals are quoted in troy ounces.

When a seller lists precious metals, it will also list them in troy ounces. This is true for most of the world, aside from parts of East Asia. In particular, the People’s Bank of China issues Gold Pandas and Silver Pandas measured in grams. Most auction and e-commerce platforms will indicate the unit of measurement as a troy ounce, but buyers often like to purchase coins with the weight and purity engraved on them. This way, there’s no question as to the actual weight of the precious metal coin.

How Much Is a Troy Ounce?

Once troy ounce equals:

How To Convert the Price of Silver (Conversion Chart)

To convert the quoted price of silver:

Grams = Mass Value x 31.1035

Avoirdupois Ounces = Mass value x 1.097

Pounds = Ounce conversion (Mass value x 1.097) / 16

Kilograms (2 options) =

• Pounds conversion ((Mass value x 1.097) / 16)) x 2.205, or
• Grams conversion (Mass Value x 31.1035 ) / 1,000

Troy Pounds = Troy Ounces / 12

Troy Oz. vs. Oz.

A troy ounce is not the same as the avoirdupois ounce used to measure common items like food or packages. Instead, it measures precious metals. A troy ounce equals 1.09714 ounces and 0.0685714 pounds. While troy ounces are heavier than conventional ounces, troy pounds are lighter than conventional pounds.

Key takeaway: Troy ounces are heavier than avoirdupois ounces.

Origin of Troy Ounce Use

There are several theories as to the origin of the troy ounce, and there may be truth to all or some of them. These beliefs include:

• It originated from Champagne fairs in Troyes, France1, which is the most widely accepted theory.
• King Offa influenced the Troy system with his silver Dirhem2.
• The exact origin is unknown, but it was heavily influenced by the Roman monetary system. This is because they measured currency in bronze bars called aes grave, which means “heavy bronze” and was equal to one pound. One-twelfth of an aes grave was uncia, or one ounce.

No matter what its origin, the troy ounce helped shape the commodities markets for hundreds of years (or longer). In 1527, it became the official unit of measurement for gold and silver in England3. On May 19, 1828, the U.S. Mint adopted the troy ounce for the regulation of coinage. Now, it’s the standard unit of measurement for all precious metals around the world, aside from parts of East Asia.

Key Takeaway: Troy ounces are used to measure precious metals in almost every country in the world.

Bottom Line

The only place you’ll run into troy ounces is in the investing of precious metals. An easy way to remember the difference between an ounce and a troy ounce at-a-glance is to know that a troy ounce is approximately 10% more than a conventional ounce. This is because one troy ounce equals 1.09714 ounces.

Sources:

1. Smith, Adam (1809). An Inquiry Into the Nature and Causes of the Wealth of Nations. Volume 1. London: T. Hamilton. p. 35. The French livre contained, in the time of Charlemagne, a pound, Troyes weight, of silver of a known finess. The fair of Troyes in Champaign was at that time frequented by all the nations of Europe, and the weights and measures of so famous a market were generally known and esteemed.

2. Skinner, F. G. (1967). Weights and measures: Their ancient origins and their development in Great Britain up to A.D. 1855. H.M.S.O.

3. Hallock, W. (1906). In Outlines of the evolution of weights and measures and the metric system (pp. 34–34). book, New York, The Macmillan company; London, Macmillan & co., ltd.

Disclosure: I/we have no stock, option or similar derivative position in any of the companies mentioned, and no plans to initiate any such positions within the next 72 hours. I wrote this article myself, and it expresses my own opinions. I am not receiving compensation for it. I have no business relationship with any company whose stock is mentioned in this article.

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