About the Gold Karat Purity Converter
This gold karat purity converter translates between the three ways gold purity is written: karats (parts out of 24), millesimal fineness (parts per thousand, the number stamped as 750 or 585) and plain percent. Pick which one you know, enter it, and the tool returns the other two along with the nearest standard hallmark.
Add the item’s weight and today’s gold spot price to see how much pure gold it actually contains and what that gold is worth at melt. That is useful when you are reading a stamp on a ring, comparing a 22k chain from India with an 18k chain from Italy, or checking whether a buyer’s offer is reasonable.
The math uses the theoretical definition — karat ÷ 24 — so 14k is 58.33% gold. Jewelers usually stamp 14k as 585 (58.5%) to stay safely above the marked karat, and the US National Stamping Act allows a tolerance of 3 parts per thousand below the mark (7 when the tested part includes solder), so real items can differ slightly from the theoretical figure.
With the default inputs, the gold purity is 58.33%. Change any value above to recalculate instantly.
How to use the gold karat purity converter
- 1Choose whether you know the karat, the fineness stamp or the percent.
- 2Enter that value — for example 18 karat or a 750 stamp.
- 3Optionally enter the item weight and choose grams, pennyweights or troy ounces.
- 4Enter today’s gold spot price per troy ounce.
- 5Read the purity, karat and fineness equivalents, plus pure gold content and melt value.
Formula and method
A karat is one twenty-fourth part, so pure gold is 24 karat and an 18-karat alloy is 18/24 = 75% gold. Millesimal fineness expresses the same fraction in parts per thousand (750), which is why European and Asian hallmarks use three-digit numbers. Percent is simply fineness divided by ten.
Pure gold content is the item weight multiplied by the purity fraction. To value it, the pure weight is converted to troy ounces (1 troy ounce = 31.1034768 g) and multiplied by the spot price, which is always quoted for pure gold. The closest standard mark is the common karat whose value is nearest to your input; hallmark stamps such as 585 and 916 are rounded up slightly from the exact 14/24 and 22/24 fractions.
- K
- Karats (0–24)
- Fineness
- Parts of pure gold per 1,000 parts of metal
- Spot price
- Price of one troy ounce of pure gold
Worked examples
10 g of 14k gold at $4,000/oz
14 ÷ 24 = 58.33% gold, so a 10 g piece contains 5.833 g of pure gold. That is 5.833 ÷ 31.1035 = 0.1875 troy ounces, worth about $750 at $4,000 per ounce.
A ring stamped 750 weighing 5 g
A 750 stamp means 750 parts per thousand, which is 75% or 18 karat (0.75 × 24). Five grams of it holds 3.75 g of pure gold, about $482 at $4,000 per ounce.
One troy ounce of 91.6% gold (22k)
91.6% × 24 = 21.98 karats, the standard “916” mark for 22k gold. One troy ounce (31.10 g) contains 28.49 g of pure gold, so its melt value is 0.916 × $4,000 = $3,664.
Frequently asked questions
What percent gold is 14k, 18k and 22k?+
Theoretically 14k is 58.33% gold, 18k is 75% and 22k is 91.67%. In practice they are usually stamped 585, 750 and 916, meaning 58.5%, 75.0% and 91.6% gold.
Why is 14k gold stamped 585 instead of 583?+
Manufacturers round up to 585 so that the alloy reliably meets the karat on the stamp after allowing for small variations in melting and solder. The extra 0.17% of gold is a safety margin, not a different standard.
What does 916 gold mean?+
916 is the fineness mark for 22-karat gold: 916 parts of pure gold per 1,000 parts of metal (91.6%). It is the most common purity for gold jewelry sold in India and the Gulf states.
Is 24k gold really 100% pure?+
Commercially, 24k means at least 99.9% (999) or 99.99% (9999) pure gold. Absolute 100% purity is not achievable in practice, so 24k items and bullion are sold at 999 or 9999 fineness.
What is the lowest karat that can be called gold?+
Since the 2018 revision, the US FTC Jewelry Guides set no karat floor for solid gold alloys: an item may be called gold as long as the correct karat immediately precedes the word, such as “9 Karat Gold”. In practice 10K is the lowest karat widely sold in the US, while 9K (375) is a standard hallmark in the UK, Ireland and Australia.
Does the alloy metal add value?+
Usually not meaningfully. The rest of a gold alloy is mostly copper, silver and zinc (or nickel and palladium in white gold), and gold buyers pay only for the pure gold content.
Results are estimates for educational purposes and are not financial advice. Rates, fees and terms vary — confirm with your lender or a licensed advisor before making decisions.