Karat Calculator: Gold Purity, Stamps and Value
This karat calculator converts between karats, purity percentages and hallmark stamps, and shows how much pure gold and what melt value any weight contains at today’s spot price of $3,883.45 per troy ounce.
Karat Calculator
Enter a karat, a purity percentage or a hallmark stamp. The other values and the gold value update instantly.
Gold Karat Chart
| Karat | Purity | Stamp | Price per gram today |
|---|---|---|---|
| 24K | 99.9% | 999 | $124.86 |
| 22K | 91.67% | 916 | $114.45 |
| 21K | 87.5% | 875 | $109.25 |
| 18K | 75% | 750 | $93.64 |
| 15K | 62.5% | 625 | $78.03 |
| 14K | 58.33% | 585 | $72.83 |
| 12K | 50% | 500 | $62.43 |
| 10K | 41.67% | 417 | $52.02 |
| 9K | 37.5% | 375 | $46.82 |
How Karats Work
A karat is one 24th part. 24-karat gold is pure; 14-karat gold is 14 parts gold and 10 parts other metals. To convert karats to purity, divide by 24 (14 ÷ 24 = 58.33%). Hallmarks express the same thing in parts per thousand, so 58.33% is stamped 585 after rounding. Karat (gold purity) is different from carat, the unit of weight for diamonds and gemstones.
Why 14K Is Stamped 585 and Not 583
The exact purity of 14K is 583.3 parts per thousand. Hallmarking standards use 585 so the stamp is a minimum guarantee with a small safety margin. Prices on this site use the exact 58.33%, which matches what refiners pay for.
From Karat to Value
Once you know the purity, value depends only on weight and the spot price. Use the full gold calculator to value several pieces with buyer payout estimates, or check the live price for each karat: 10K, 14K, 18K, 22K and 24K.
Related: gold hallmarks guide, what is 14K gold, gold price per gram
Frequently Asked Questions
How do you calculate gold karat purity?
Divide the karat by 24. 18K ÷ 24 = 75% gold; 10K ÷ 24 = 41.67% gold.
What karat is 585 gold?
585 is 14K gold, 58.5% pure by the stamp and 58.33% exactly.
What karat is 750 gold?
750 is 18K gold, 75% pure.
Is karat the same as carat?
No. Karat measures gold purity; carat measures the weight of gemstones (1 carat = 0.2 grams).