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Gold Weights and Measures


The purpose of this article is to acquaint you with some of the terms used in weighing, measuring and calculating quantities of gold. It is useful if you are interested in understanding more about what is involved in the buying and selling of gold.

You can use this information...

To better understand the relationship between weight, fineness (or purity) and content of gold coins and other gold objects.

When selling your gold coins, jewelry or "scrap" gold
- when a dealer quotes you a price for your gold by pennyweight or gram, this information can help you calculate what discount s/he is offering in relation to the spot price of gold.

To help (and impress!) your friends and family members - who want to buy gold or are interested in selling their gold coins or jewelry and don't have the slightest idea of what it is worth or how to proceed.

Let's get started...

The Troy Weight System

The Troy weight system is the universal system used to weigh gold (and silver). Unlike the Avoirdupois weight system, the system commonly used in the United States that is based on 16 ounces to the pound, the Troy weight system is a series of units of weight based on a pound of 12 ounces and an ounce of 20 pennyweights or 480 grains.

Under the Troy system...

1 grain (the smallest unit) = 0.042 pennyweight; metric equiv. = 0.0648 grams
1 pennyweight = 24 grains = 0.05 ounces; metric equiv. = 1.555 grams
1 ounce = 20 pennyweight = 480 grains; metric equiv. = 31.103 grams
1 pound = 12 ounces = 240 pennyweight; metric equiv. = 0.373 kilograms

To see how this weight system is used as it relates to gold, lets look at two popular gold coins - the Gold American Eagle and the gold Canadian Maple Leaf. Each contain one Troy ounce of fine gold. The Maple Leaf has a gold fineness or purity of .9999. Since this coin is pure gold, its gross weight and net gold weight are both one Troy ounce or 31.103 grams.

The Gold American Eagle is not pure gold. It is alloyed for hardness and has a gold fineness of .9167. In order for this coin to contain one Troy ounce of gold, the gross weight has been increased to 1.0917 Troy ounces or 33.956 grams.

The Avoirdupois Weight System

Under the Avoirdupois system...

1 grain (the smallest unit) = 0.036 drams; metric equiv. = 0.0648 grams
1 dram = 27.343 grains = 0.0625 ounces; metric equiv. = 1.771 grams
1 ounce = 16 drams = 437.5 grains; metric equiv. = 28.349 grams
1 pound = 16 ounces = 7,000 grains; metric equiv. = 0.453 kilograms

You can convert Avoirdupois to Troy ounces by multiplying Avoirdupois oz. times 0.911

You can convert Troy ounces to Avoirdupois ounces by multiplying Troy oz. times 1.097 

The Gold Karatage System

Most gold jewelry uses the Karatage system to define the gold content in the piece. It is used to to identify the fineness or purity of gold as a fraction of 24 parts. Pure gold (or fine gold) is 24 karats which has a fineness of .9999 or 99.99%. Sometimes gold content is expressed in parts per thousand so if you see 500 stamped on your gold jewelry, it is an alloy containing 50% gold.

You can use the following Karatage list as a guide to for determining gold fineness and percentages in the U.S.

24 karats = .9999 fineness = 99.99% gold purity
22 karats = .9167 fineness = 91.67% gold purity
18 karats = .7500 fineness = 75.00% gold purity
14 karats = .5833 fineness = 58.30% gold purity
12 karats = .5000 fineness = 50.00% gold purity
10 karats = .4166 fineness = 41.66% gold purity

Let's say you have a piece of gold jewelry you are interested in selling. You see a 18K stamp on the jewelry so you know it is 75% pure gold. Since gold is such a soft metal, the remaining 25% is likely one or more metals to "harden" the piece of jewelry, add color to it or both.

Most dealers will quote you a price for your gold by gram or pennyweight, taking into account the gold fineness. So, in the example above, they will give you a price of what they are paying for an 18K piece of jewelry based on the weight and a gold fineness of .7500 or 75% purity.

The question then becomes "Is that a fair deal? What percent discount is their offer in relation to the spot price of gold?" That is the subject of a another article - Selling Your Scrap Gold.


Disclaimer: I have made every reasonable effort to produce an informative and helpful article on Gold Weights and Measures based on my research and experiences. However, I make no representation or warranties of any kind with regard to its completeness, accuracy or suitability for any specific situation or purpose. See our Terms & Conditions for more info.

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