Learning Resources
Weighing Units Explained
Precious metals are bought and sold in units most people never meet anywhere else. Mixing them up is one of the easiest ways to misjudge what your items are worth, so here is the whole vocabulary in one place.
- Gram (g): the unit to start with. Simple, universal, and what most online gold calculators expect.
- Troy ounce (ozt): 31.1 grams. This is the unit gold and silver are quoted in worldwide. When you read that gold is at $4,500 an ounce, this is the ounce being talked about.
- The regular ounce (oz): 28.35 grams. Also called the avoirdupois ounce, and it is what a kitchen or postal scale means by ounce. Nearly 10% lighter than a troy ounce. Never price precious metal with it.
- Pennyweight (dwt): 1.555 grams. Twenty of them make one troy ounce.
- Carat (ct): 0.2 grams, for gemstones only. Not to be confused with karat, spelled with a K, which measures the purity of gold.
- Grain (gn): 0.0648 grams, with 480 to a troy ounce. Rare in the jewelry trade today, but it turns up in older coin specifications.
- Tael (tl): an East Asian unit of roughly 37.8 grams, though it varies by region. You will meet it with Chinese gold bars and jewelry, and almost never otherwise.
Why Pennyweight Is Abbreviated dwt
There is no d anywhere in the word, which is exactly why the abbreviation confuses everybody. It comes from the Latin denarius, a Roman silver coin. The medieval English penny was modelled on it, so d became the standard shorthand for a penny, the same d that appeared in British prices right up until decimalisation in 1971. So dwt is literally denarius weight: penny weight.
This matters to you because a great many American gold buyers quote per pennyweight rather than per gram. A price per pennyweight will always look larger than a price per gram for exactly the same gold, simply because a pennyweight is a bigger unit. Before you get excited about a number, check which unit it refers to.
The Conversions Worth Remembering
- 1 troy ounce = 31.1 grams = 20 pennyweight
- 1 pennyweight = 1.555 grams
- 1 regular ounce = 28.35 grams
- 1 carat = 0.2 grams
- Grams to pennyweight: divide by 1.555
- Grams to troy ounces: divide by 31.1
Weigh in grams, then convert. Grams are the least ambiguous number you can write down, and every other unit on this list is one division away.