Gold purity is measured in karats (or carats outside the U.S.). This system indicates the proportion of pure gold in a piece of metal, on a scale of 24. A higher karat number indicates a higher percentage of pure gold in the alloy.

• 24K is considered 99.9% pure gold. It’s the most valuable but is very soft, making it unsuitable for most everyday jewelry.
• 22K (916) gold: 91.6% pure, mixed with metals for durability.
• 18K is 75% pure gold, and its higher alloy content makes it very durable and a popular choice for rings and other pieces worn daily.
• Lower karats: more added metals for durability. Choose based on your needs: luxury, durability, or affordability.

Purity can also be expressed in “millesimal fineness,” a three-digit number that represents parts per thousand (e.g., 750 for 18K gold).