Thursday, August 21, 2014

Rick’s Pedigree Coins – Weighing Precious Metals – Troy vs. Avoirdupois Ounce

I thought I would switch it up a little bit and write a few articles on some other coin topics that the Pedigree collector may find of value.  The first thing to cover is the weight issue when purchasing precious metals.  When measuring the weight of gold or silver, the Troy ounce is used.  When measuring the weight of a person, pound of beef or chicken, the Avoirdupois ounce is used.  While both are measured in ounces, that is where the similarities stop.

Precious metals and gemstones (including gold, platinum, silver) are measured using the Troy measurement system.  A Troy ounce contains 31.10 grams and 12 ounces equal 1 Troy pound.  All other items (fruits, vegetables, people, animals, etc) use the Avoirdupois ounce.  An Avoirdupois ounce contains 28.35 grams and 16 ounces equal 1 Avoirdupois pound.  In practice when talking about weight, the descriptive “avoirdupois” is dropped; however to avoid misunderstandings, when referring to precious metals the Troy ounce description is often retained.  If you are purchasing gold or any other precious commodity and it is not described as a Troy ounce, you should ask for clarification for your own protection.  After all, a Troy ounce of gold weights 2.75 grams more than an Avoirdupois ounce and at the current price of gold that equals a $115 difference per ounce.  

A bit of a brainteaser is that a Troy ounce weights more than an Avoirdupois ounce.  But a Troy pound weights less than an Avoirdupois pound.  (Troy pound = 31.10 grams X 12 oz to a pound = 373.2 grams).  (Avoirdupois pound = 28.35 grams X 16 oz to a pound = 453.6 grams). 

Source for this article:  Mike Unser,, July 22, 2007

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