Gold karat calculator
Enter the karat or the fineness stamp of a gold item and its weight. The calculator shows the purity in percent, the matching fineness or karat, and how many grams and troy ounces of pure gold the item contains.
Runs in your browser: nothing you enter is sent anywhere.
How to use it
- Choose karat or fineness and enter the value from the stamp.
- Enter the weight of the item in grams.
- Read the pure gold weight, the purity and the matching fineness or karat.
- purity = karat / 24 = fineness / 1000
- pure gold (g) = weight × purity
- troy ounces = grams / 31.1034768
- karat = fineness × 24 / 1000
Worked example
A 10 g bracelet stamped 585: purity 585 / 1000 = 58.5 %, which is 14.04 karat. It holds 10 × 0.585 = 5.85 g of gold, about 0.188 troy ounces, and 4.15 g of other metals.
Tips
- Weigh without stones: gems add weight but no gold.
- The scrap value is the pure gold weight times the price per gram of pure gold, minus the buyer’s margin.
Frequently asked questions
How much gold is in 14K or 18K?
Karat counts parts of gold in 24. 18K is 18/24 = 75 % gold, 14K is 14/24 ≈ 58.33 %, 10K is 41.67 % and 24K is pure gold. A 10 g 18K ring contains 7.5 g of gold.
What do 585, 750 and 916 stamps mean?
They are fineness: parts of gold per 1000. 750 is 75 % (18K), 916 is about 22K and 375 is 9K. 585 is 58.5 %, which is 14.04K: makers stamp 585 for 14K so the item is never below the nominal purity of 58.33 %.
How do I convert grams of gold to troy ounces?
Divide by 31.1034768, the number of grams in one troy ounce. 7.5 g of pure gold is 0.24113 oz t. Gold prices are usually quoted per troy ounce of pure gold.
What are the other metals in gold jewellery?
Mostly silver, copper and zinc; white gold may contain palladium or nickel. They make the piece harder and change its colour. The calculator shows their total weight, not which metals they are.