‘What’s a troy ounce?’ Avoirdupois vs Troy, Explained

Newcomers are often surprised that “ounces” and “pounds” have a completely different meaning in the bullion market. The units of weight we learn in school and use for everything from groceries to postage to body mass are based on the avoirdupois system. However, precious metals (and gemstones) are weighed using the troy system – which also uses pounds and ounces as units.
There are 12 troy ounces in every troy pound and 16 ounces in every avoirdupois pound. Troy ounces are heavier than ounces, but troy pounds are lighter than pounds. Comparing the two systems sounds confusing, but it’s easier to understand using the metric system:

Troy Ounces (ozt.) > Avoirdupois Ounces (oz.)

  • 1 troy ounce = 31.1035 grams
  • 1 avoirdupois ounce = 28.3495 grams
  • With a difference of 2.754 grams, a troy ounce is around 10% heavier

Troy Pounds (lb t.) < Avoirdupois Pounds (lb.)

  • 1 troy pound = 12 troy ounces = 373.242 grams
  • 1 avoirdupois pound = 16 avoirdupois ounces = 453.592 grams
  • With a difference of 80.35 grams, a troy pound is lighter by 2.83 avoirdupois ounces.

After ounces, the next smallest unit of measure in the troy system is the pennyweight (dwt). One troy ounces contains 20 pennyweights. At MGS, we want to pay you for every bit of precious metal in your lot, so we pay by the pennyweight. If you need help converting the weight of your precious metals, use our weight conversion calculator, or download our app, to make estimates and sales easier.

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