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Troy Ounce vs Ounce - learn the difference

Troy Ounce vs Ounce

If you collect silver or gold Bullion, you may be aware of the Troy Ounce, a measurement that is commonly used in conjunction with bullion metals. But how does a Troy Ounce different from a regular ounce – and who, or what, is Troy? Before learning about the history of the Troy Ounce and how it came to use in Bullion trading today, one must first understand how a Troy Ounce is different from a standard ounce.

A Troy Ounce:

  • Is 2.75 grams more than a regular ounce
  • Weighs 31.1034768 grams while a regular ounce weighs 28.3495231 grams
  • Is 480 grains, versus 437.5 grains for a regular ounce

So, for example, one Troy Ounce of gold weighs more than one ounce of sugar. In other words, A Troy Ounce is not a conventional ounce, as most people would think. As a matter of fact, the weights of bullion metals are, generally, calculated on a different weight scale than anything else.

Why should this matter to you? If you are purchasing 100 ounces of gold and it weighs the same as 100 ounces of sugar, you are losing out on 8.85 Troy Ounces of metal – that’s a lot of gold! So, when purchasing silver or gold Bullion, always make sure that the weight is being calculated using a Troy Ounce scale.

Units of Measurement in the Troy Weight System

The Troy Ounce is a standard of measurement in the Troy Weights System, which is based on 12 Troy Ounces equaling one Troy pound. This is, of course, quite different from the everyday weight system used in the United States, where 16 ounces equals one one pound – that system is called Avoirdupois System.

If one Troy Ounce is equal to 480 grains, then one Troy Pound comes to 5,760 grains. Meanwhile, a standard Pound comes to 7,000 grains – 21 percent heavier than a Troy Pound!

Pennyweight, as you may have guessed, has connections to the old British monetary system, which was, until 1971, reliant upon a derivation of the Troy Weights System, which will be discussed in a bit more detail below.

A pennyweight (dwt) is equal to 24 grains, and 20 dwt comes to one Troy Ounce. Extrapolating that forward, 240 dwt is one Troy pound. This is all based on the old British Pound (the unit of currency, that is), being equivalent in value to 240 Pence.

So, in other words:

  • A Shilling represented 12 Pence…
  • An ounce came to 20 Pence…
  • And a Pound came to 12 ounces or 20 Shillings!


But, wait, why is there a “d” in dwt – which is the signature for pennyweight? The “d” stands for Denarius which is an ancient Roman coin that appears frequently in the New Testament of the Holy Bible and is equivalent to a Penny, the base coin of many monetary systems.

How Did the Troy Ounce Come into Existence – and Why?

The Troy system came into being in England during the 1400s and was adopted as the official standardization of measuring gold and silver in 1527. During the 19th century, the British Empire ended the use of the 12-ounce Troy Pound, but the Troy System remained in used both in Britain and America for measuring Bullion.

Interestingly, in both the Troy Weight System and the Avoirdupois System, it is stipulated that a grain weighs 0.06479891 gram, as defined by the international yard and pound agreement of 1959.

It is important to remember that the Troy Weight System is largely used in defining the weight of only gold, silver, and gemstones – Troy weight is not generally used for other purposes.

Where Does the “Troy” in “Troy” Ounce Come From Anyway?

Was Troy a person, place, thing? The name is believed to have originated at the Champagne fairs held at Troyes, in northeastern France. Troy, as a unit of measurement, may have hailed from a more northern region of Europe. It is thought the British Troy system may have been a derivation of the Troy weight system of Bremen, in which the Bremen Troy Ounce had the equivalent of 480.8 British Imperial grains.

Conversely, one school of thought suggests Troy is not linked to a French town, but, rather, a dialect word “troi,” which means balance. In this manner, Troy would refer to a manner of weighing items such as bullion or medicines, among other small valuables.

Some scholars think that Troy weight system may be related to a weight standard common in the Muslim world, in which the Gold Dirhem weighs 47.966 British Imperial grains. This is similar to English King Offa’s weight standards, which have roots in the Silver Dirhem – which equals 45 British grains. King Offa’s silver penny replaced the Sceat and was worth half of a Silver Dirhem.

As a side note, the Scottish system of weights and measurements used a system dependent on multiples of 16 (which may strike most Americans as vaguely familiar). 16 drops equaled a Troy Ounce, 16 ounces came to a Troy Pound, and 16 Troy Pounds represented the Troy Stone. The pound came to 7,716 British Imperial grains, but once Scotland came into union with the British Empire, was rounded to 7,680 British Imperial grains. This comes to 16 ounces, containing 16 drops, with each drop weighing 30 grains. The rounding brings the ounce and grain in line with the English standard.

Regardless of the name origin of the Troy Ounce, it has remained in use for at least seven centuries and likely will remain in use for a long time to come.