How to convert 21K gold to 12K
21K gold is 87.5% pure and 12K gold is 50.0% pure. To find the 12K weight with the same gold content, multiply the 21K weight by 0.875 and divide by 0.5. One gram of 21K equals 1.75 grams of 12K.
Example
10 g of 21K gold contains 8.75 g of pure gold, the same as 17.5 g of 12K. Today 10 g of 21K is worth $1,165.
When you need this conversion
- Exchanging old jewelry for new pieces in a different karat.
- Comparing prices quoted per gram of 22k with prices quoted for 18k or 24k.
- Planning how much of a karat a jeweler needs to remake an item.
Note that remaking jewelry involves melting losses and labor, so a jeweler's exchange rate is usually below this pure-gold equivalent. See methodology.