The weight of a gold coin can vary considerably, ranging from as small as 1/20th of a gram to as large as a metric ton.
However, the most common and standard weight for gold coins, especially bullion coins, is one troy ounce. A troy ounce, a measurement system specifically used for precious metals, is equivalent to 31.1035 grams.
It’s important to differentiate a troy ounce from a standard or avoirdupois ounce, which is slightly lighter at 28.3495 grams. Gold coins, particularly those like the American Gold Eagle , may have a slightly heavier overall weight than one troy ounce of pure gold due to being alloyed with other metals (like copper and silver) to enhance durability. In such cases, the stated weight of the coin refers to its pure gold content. For instance, a 1 oz American Gold Eagle coin has a total weight of 33.931 grams, containing 1 troy ounce (31.1035 grams) of pure gold along with other metals.
Common fractional sizes of gold coins also exist, including 1/2, 1/4, and 1/10 troy ounces, [according to JM Bullion].
