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What a troy ounce is (the unit gold and silver actually use)
A troy ounce is 31.1035 grams. It is the unit for gold, silver, and platinum. It is heavier than a grocery-store ounce.
A troy ounce is the unit of weight for precious metal.
It equals 31.1035 grams. There are twelve troy ounces in a troy pound. Coin shops almost never say “troy pound.” They say ounces and grams.
It is not the kitchen ounce
The everyday US ounce is 28.35 grams. If you weigh a one-ounce gold coin on a food scale, the number will look wrong. The unit is wrong, not the coin.
The shop-floor version of this fight is here: troy vs regular ounce. This page is the definition.
Where you will see it
Spot prices are dollars per troy ounce. Bar stamps say 1 oz, 10 oz, or 1 kilo. Eagle, Maple, Krugerrand, and Libertad specifications are in troy ounces. Jewelry tickets often start in grams or pennyweight and get converted.
COMEX and LBMA. Karat math. What a kilo bar is.
More on the coin and money library.
Extra pad history for the troy ounce
Troy weight is a leftover from the old trade in precious metal. Twelve troy ounces make a troy pound. Shops almost never say troy pound. They say ounces and grams. One troy ounce is 31.1035 grams. The kitchen ounce — avoirdupois — is 28.35 grams. If you weigh a one-ounce gold coin on a food scale, the number will look wrong. The unit is wrong, not the coin. The shop-floor fight is on troy vs regular ounce.
Spot is dollars per troy ounce. Bar stamps say 1 oz, 10 oz, or 1 kilo (1,000 grams, about 32.15 troy ounces). Eagle, Maple, Krugerrand, and Libertad specs are troy.
What the shop does with units on the ticket
Jewelry often starts in grams or pennyweight and gets converted. 20 pennyweight is one troy ounce. Ask if you see “dwt.” It is not a trick if they tell you. The scale should be on zero with the empty tray. The unit should be visible. Weigh and test in front of you.
If they convert in their head and will not show the raw weight, ask them to write the raw weight down. Karat still matters: 31.1 grams of 24k is about an ounce of gold. 31.1 grams of 14k is not. COMEX and LBMA speak troy. So does this pad.
People also ask
Why doesn’t a one-ounce Eagle weigh 28 grams? Because it is a troy ounce, and a 22k Eagle is heavier than one ounce of fine gold.
Is a kilo 32 ounces? About 32.15 troy ounces.
Can I use a food scale? You can. Do not argue from it.
What is pennyweight? Old jewelry unit. 20 dwt = 1 troy ounce.