Examine your gold jewelry carefully to find the markings that denote the karatage. These numbers are super tiny, so get out a magnifying glass if you're having a hard time. If the jewelry was made in the U.S., it will be marked 14k, 18k and so on. Most jewelry is either 14k or 18k, but you might see numbers between 10k and 24k. If the jewelry was made in Europe, there's going to be a little three-digit number that tells you what the percentage of gold in your jewelry is. For example, a 14k piece of jewelry is marked as "583" and an 18k piece is marked as "750."
Weigh your gold jewelry using a scale that measures in grams. Use a digital scale for the most accurate reading. A bathroom scale is no good for this project -- use a small kitchen scale. Write down the total weight of the piece of jewelry on a piece of paper.
Figure out the decimal that corresponds to the karatage or percentage of gold. Here's how the percentages break down: 24k is 100 percent, 22k is 91.7 percent, 18k is 75 percent, 14k is 58.3 percent, 12k is 50 percent and 10k is 41.7 percent. To find the corresponding decimal for each karat amount, you just have to slide the decimal point two spaces to the left. For example, the decimal for 18k gold is 0.75. It's really that simple!
Multiply the total weight of your gold jewelry by the decimal figure that corresponds to its karatage. So, let's say you have a 14k gold bracelet that weighs 100 grams. Multiply 100 times 0.583 to get 58.3 grams. The karat weight of your gold bracelet is 58.3 grams. Who said math wasn't fun?