How to Measure Gold in Carats & Ounces


Gold has been much in the news lately, with the price of the precious yellow metal rising steadily in recent years to around $1,500 an ounce as of May 2011. But what do we really mean by "gold" and, for that matter, what do we really mean by an "ounce"? Understanding the terms that gold collectors and jewelers use to measure the purity and the weight of gold, namely carats (or karats) and ounces is important when determining the value of gold coins or jewelry.

Things You'll Need

  • Magnifying glass
  • Laboratory test scale
  • Calculator

Measuring Gold in Carats

  • Use carat, usually spelled "karat" in the United States, to measure the purity of gold. Pure gold is 24 carats; an alloy three-quarters gold, one-quarter other metals is 18 carats, and half gold and half another metal is 12 carats.

  • Examine gold jewelry under a magnifying glass to find a small stamped number followed by the letter "k". That is the carat purity of the gold in the item. Look on the face of gold bars for a four-digit number, indicating the degree of purity, with "9999" meaning 99.99 percent pure gold. This is as close to pure gold as you'll find.

  • Consult a certified gold appraiser, who has the specialized equipment and expertise, to properly test the gold content of coins, bars and jewelry, and guarantee that the purity number stamped on the gold reflects the content.

Measuring Gold in Ounces

  • Measure the gold in troy ounces, the kind used to weigh precious metals, and not in avoirdupois ounces, the kind you'll see in the supermarket. Remember that a troy pound is 12 ounces (about 373 grams), not the avoirdupois 16 ounces (454 grams) which is more commonly recognized.

  • Use a sensitive scale, such as a laboratory scale, which measures in grams and tenths of grams. To convert the result to troy ounces, divide the weight in grams by 31.1. Have a certified testing laboratory with the proper equipment, as an alternative, perform the work.

  • Calculate the value of your coin, gold bar or jewelry. Take the purity reading you made in Section 1 and multiply that number, which represents the percentage of gold in the item, by the item's weight determined in Section 2. Record the result. Multiply that result by the current per-ounce price of gold to determine the total value of your item. For instance, a 12-carat piece of jewelry that weighed 62.2 grams contains 1 troy ounce of gold, which is worth around $1,500 American dollars as of May 2011.

Tips & Warnings

  • Gold, a soft metal, is often alloyed with other metals to make jewelry harder (and much cheaper).
  • Should you want to judge that pound of chicken cutlets against a pound of gold: 14.583 troy ounces equals 16 avoirdupois ounces, or 1 pound.
  • Don't confuse gold carats with gem carats -- the latter really is a weight measure, used to judge the size of precious stones.
  • One place to start looking for a certified appraiser is the American Society of Appraisers website; another may be consulting your coin-collector friends who have used appraisers.
  • Don't expect jewelers and gold buyers to pay half the market rate, say, for that 12-karat bracelet; buyers often have to pay brokerage and refining fees, along with overhead such as rent and wages, and will want to make a profit, too.

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