How to convert 18K gold to 20K
18K gold is 75.0% pure and 20K gold is 83.3% pure. To find the 20K weight with the same gold content, multiply the 18K weight by 0.75 and divide by 0.833. One gram of 18K equals 0.9004 grams of 20K.
Example
10 g of 18K gold contains 7.5 g of pure gold, the same as 9.0036 g of 20K. Today 10 g of 18K is worth $998.39.
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.