How to Calculate Penny Weights for Selling Gold

by Diane Perez

The British standardized the pennyweight measure in 1878. It equals 1/20 Troy ounce and is abbreviated DWT. Dealers buy and sell gold by the ounce yet some professionals, including dentists and laboratories, measure their gold by pennyweight. If you plan to sell gold jewelry or artifacts, then you have a few additional calculations to make before you convert pennyweights to ounces. This is because pure gold is too soft a metal for jewelry and artistic creations, so it is bonded with a base metal to strengthen it. The base metal part of your jewelry has no value.

1. Separate your gold by its karat weight, such as 14k and 18k. A karat represents the percentage of gold in an item. Pure gold is 24 karats. A magnifying glass will help you to read some of the obscure numbers.

2. Calculate the amount of gold present in each group by dividing the number of karats by 24. For example, to calculate the amount of gold in 18-karat jewelry: 18 / 24 = .75. This means that your 18k jewelry is 75 percent gold.

3. Place the first group of gold on the scale and note the weight. Multiply that weight by the percentage of gold it contains. To continue the above example, if the weight on the scale was 60 pennyweights: 60 x .75 percent = 45 pennyweights actual gold.

4. Repeat this process for each group of gold. Do not include gold-plated items, as they only have a thin coating of gold electroplated to a base metal. These items are mostly base metal. While some gold-plated artifacts may have historical value, they are not considered precious metals.

5. Convert pennyweight into ounces. It takes 20 pennyweights to equal 1 ounce, so divide the pennyweight of your gold by 20. Using the above example: 45 pennyweight gold / 20 = 2.25 ounces gold.

6. Research the current price of gold and multiply that amount by the number of ounces you wish to sell. As an example: $1,700 / ounce selling price x 2.25 ounces gold = $ 3,825. The jeweler will not pay this price, as he takes a portion to cover his overhead and profit. However, you need to know the value to determine if the purchase offer is fair.


  • To convert ounces to pennyweight, simply multiply by 20. For example: 2 ounces gold x 20 = 40 pennyweight gold.

Items you will need

  • Magnifying glass
  • Pennyweight jewelry scale
  • Calculator

Photo Credits

  • Sam Robinson/Photodisc/Getty Images