Gold Karat Purity Converter
Convert a gold karat into purity percent and millesimal fineness, or turn a hallmark stamp like 585 or 750 back into karats. Add the item's weight to see how much pure gold it holds.
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From 1 to 24 (24K = pure gold)
The 3-digit stamp, e.g. 417, 585, 750, 916, 999
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How to use the Gold Karat Purity Converter
- Pick what you know: a karat, a purity percent or a fineness stamp.
- Enter the value, for example 14 karat or the stamp 750.
- Add the item weight (optional) in grams, troy ounces or pennyweight.
- Read the result: purity, fineness, nearest standard stamp and pure gold content.
- Check the chart to compare all standard karats, or download it as CSV.
Karat to purity formula
Karat measures gold purity in 24ths. Pure gold is 24 karat, so each karat is 1/24 of the metal by weight, or about 4.17%.
purity % = karat ÷ 24 × 100 · fineness = karat ÷ 24 × 1000 · karat = fineness × 24 ÷ 1000
Example: 18K gold is 18 ÷ 24 = 0.75, so it is 75% gold and carries the stamp 750. Going the other way, a ring stamped 585 is 585 × 24 ÷ 1000 = 14.04 karat, which is 14K. To find the pure gold in an item, multiply its weight by the purity: a 5 g 14K ring contains 5 × 0.5833 = 2.92 g of gold (0.094 troy ounces).
Gold karat, purity and hallmark chart
| Karat | Gold purity | Exact fineness | Usual stamp | Where you see it |
|---|---|---|---|---|
| 8K | 33.33% | 333.3 | 333 | Minimum gold in some European countries |
| 9K | 37.5% | 375 | 375 | Common in the UK and Ireland |
| 10K | 41.67% | 416.7 | 417 | Lowest karat sold as gold in the US |
| 12K | 50% | 500 | 500 | Half gold; older and costume pieces |
| 14K | 58.33% | 583.3 | 585 | Most popular US jewelry grade |
| 15K | 62.5% | 625 | 625 | Antique British grade (discontinued) |
| 18K | 75% | 750 | 750 | Fine jewelry and watch cases |
| 20K | 83.33% | 833.3 | 833 | Some Asian jewelry |
| 21K | 87.5% | 875 | 875 | Popular in the Middle East |
| 22K | 91.67% | 916.7 | 916 | Bullion coins and South Asian jewelry |
| 23K | 95.83% | 958.3 | 958 | Gold leaf and Thai jewelry |
| 24K | 100% | 1,000 | 999 | Investment bars and pure gold |
Stamps such as 585 and 916 are rounded from the exact fractions so the mark is a guaranteed minimum. 999 is often called "three nines" fine gold; investment bars may be 999.9 ("four nines").
Tips for reading gold marks
- K, KT and ct are the same thing. 14K, 14KT and 14ct all mean 14 parts gold out of 24. Don't confuse karat (purity) with carat (a gemstone weight of 0.2 g).
- Plated or filled marks are not solid gold. GP, GEP and HGE mean a thin plating; GF or 1/20 14K GF means gold-filled, where only about 5% of the weight is 14K gold.
- Color does not change karat. Yellow, white and rose 14K all hold 58.3% gold; only the other metals (silver, copper, palladium, nickel) differ.
- Weigh without stones. Gems, pearls and steel clasp springs add weight that is not gold, so subtract them before estimating gold content or scrap value.
Frequently asked questions
How do you convert karat to purity?
Divide the karat by 24 and multiply by 100. For example, 14K is 14 ÷ 24 × 100 = 58.33% gold, and 18K is 75% gold.
What does 585 mean on gold?
585 is the fineness stamp for 14 karat gold. It means the metal contains at least 585 parts gold per 1,000 (58.5%). The exact 14K fraction is 583.3, rounded up so the mark is a guaranteed minimum.
What karat is 750 or 916 gold?
750 is 18 karat (75% gold). 916 is 22 karat (91.6% gold), the grade used for many bullion coins and South Asian jewelry.
Is 24K gold 100% pure?
24 karat means all 24 parts are gold. In practice investment gold is 99.9% (999) or 99.99% (999.9) pure because tiny traces of other elements remain after refining.
How much pure gold is in a 10 gram 14K chain?
Multiply the weight by the purity: 10 g × 0.5833 = 5.83 g of pure gold, which is about 0.188 troy ounces.
What is the lowest karat that can be called gold?
In the United States, the FTC Jewelry Guides say an item below 10 karat should not be described as gold. Some countries allow 8K or 9K.
Is karat the same as carat?
No. Karat (K) is gold purity in 24ths. Carat (ct) is a gemstone weight unit equal to 0.2 grams. In British English "ct" is also used for gold purity, so 9ct gold means 9 karat.
Are all the tools on FreeToolCabin tested for quality and accuracy?
Yes! Every tool on our site undergoes automated Q/A testing in real browser environments to ensure high precision, correct output, and zero errors. If you happen to spot a bug or have a suggestion, please contact us at [email protected] and our team will review it right away.