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A complete reference to the karat system — how gold purity is measured, hallmarked, and why different markets standardise on different purities from 9K to 24K.
The karat (abbreviated K or kt; spelled carat in British English when referring to gold purity) is a unit of purity for gold alloys. It divides gold into 24 equal parts. Pure gold is therefore 24 karats (24K), meaning all 24 parts are gold. An 18K alloy contains 18 parts gold and 6 parts other metals — a gold content of 75%.
The system traces back to the medieval Arabic qirat (قيراط), a carob seed used as a counterweight, which weighed approximately 0.2 grams. Arabic traders used 24 qirat as the standard weight of a gold coin, and the purity system that emerged from this practice still governs global gold commerce today.
Fineness is the metric alternative: it expresses gold content in parts per 1,000. 24K = 999 fineness (sometimes written 999.9 for four-nine investment gold), 22K = 916 fineness, 18K = 750 fineness. European assay offices stamp fineness marks because they are unambiguous in a multi-language context.
| Karat | Gold % | Fineness | Common Hallmarks | Primary Market Use |
|---|---|---|---|---|
| 24K | 99.9% | 999 | 999, 999.9, 24K | Bullion, coins, bars |
| 23K | 95.8% | 958 | 958 | Rare; some Middle Eastern pieces |
| 22K | 91.7% | 916/917 | 916, 917, 22K | Gulf, India jewelry (dominant) |
| 21K | 87.5% | 875 | 875, 21K | Egypt, Levant, East Africa |
| 20K | 83.3% | 833 | 833 | Rare; some Gulf antiques |
| 18K | 75.0% | 750 | 750, 18K | Europe, Americas, fine jewelry |
| 16K | 66.7% | 667 | 667 | Very rare, historical |
| 14K | 58.3% | 585 | 585, 14K | US, Eastern Europe, everyday jewelry |
| 12K | 50.0% | 500 | 500 | Rare |
| 10K | 41.7% | 417 | 417, 10K | US minimum legal 'gold'; fashion jewelry |
| 9K | 37.5% | 375 | 375, 9K | UK, Australia, Ireland minimum for gold |
| 8K | 33.3% | 333 | 333 | Germany historical, some European markets |
| 6K | 25.0% | 250 | 250 | Decorative items, gold-filled |
Karats shown in bold rows are the primary commercial standards used in international jewellery trade. Rows without bold are rare or historical.
Gold purity preferences are shaped by centuries of trade tradition, religious context, regulation, and consumer culture. Understanding these differences matters when comparing prices across borders or evaluating the value of inherited jewellery.
22K gold — known in the region as "Saudi gold" or "Arabian gold" — has been the commercial standard in Gulf jewelry markets for generations. At 91.67% purity, the 8.33% alloy (typically copper and silver) gives the metal enough hardness for intricate filigree work while retaining the deep yellow hue that Gulf consumers prize. Islamic financial tradition values near-pure gold as a store of wealth, making 22K an acceptable compromise between purity and workability. The Gulf gold souq system, most famously Dubai Gold Souk, is built almost entirely around 22K, and regional assay offices hallmark accordingly.
Egypt standardised on 21K (875 fineness) as the minimum commercial purity for gold jewellery. The Egyptian Assay Office requires hallmarking, and 21K pieces bear the '875' stamp. This karat offers a balance between the deep colour of 22K and the durability of 18K, making it ideal for the heavy, ornate bridal jewellery that dominates the Egyptian market. Jordan and Lebanon followed similar conventions due to cultural and trade ties. Egyptian gold jewellery is widely exported across North Africa, the Levant, and the Gulf diaspora market, spreading the 21K standard further afield.
18K (750 fineness) is the dominant standard for fine jewellery across most of Europe. The 25% alloy content — typically combinations of copper, silver, palladium, or zinc — allows goldsmiths to create harder, more durable alloys suitable for stone settings and intricate prong work. White gold (18K with a palladium or nickel alloy) and rose gold (18K with a copper-heavy alloy) both owe their colour characteristics to this karat. Italy, the world's largest fine gold jewellery exporter, primarily manufactures in 18K. The EU hallmarking directive recognises 750 as the primary fine-gold fineness.
14K (585 fineness) is the most common karat in the American and Canadian jewellery market, though 18K and 10K are also prevalent. The FTC requires a minimum of 10K to be marketed as 'gold' in the US. 14K offers excellent durability for everyday rings, bracelets, and earrings, and its lower gold content makes it more price-accessible than 18K without sacrificing the 'gold' quality perception. High-end American jewellers use 18K; mass-market chains predominantly use 14K.
9K (375 fineness) is the minimum legal standard for gold jewellery in the UK and Ireland — a legacy of 19th-century hallmarking law. British consumers have historically accepted lower-purity gold because robust hallmarking institutions (the London, Birmingham, Edinburgh, and Dublin Assay Offices) guarantee the stated purity. Australia also trades heavily in 9K for budget jewellery. 9K white gold is particularly popular for everyday engagement rings in these markets.
Every commercially sold gold piece should bear a hallmark — a stamp applied by an assay office or manufacturer certifying purity. Key things to look for:
When using Serafa's gold calculator, enter the piece's weight and select its karat. The calculator applies the purity factor to the current 24K spot price per gram. For example, with a gold spot price of $90.00 per gram (24K):
This intrinsic value — the raw metal value — is also called the "melt value." It represents what a refiner would theoretically pay if the piece were melted and its gold extracted. The actual resale value at a jeweler or pawn shop will be lower (typically 60–80% of melt value) due to the dealer's processing costs and margin.
A karat is a unit measuring gold purity on a scale of 24. It represents how many parts out of 24 are pure gold. 24 karats (24K) means 100% gold (99.9%+ fineness); 18K means 18 parts gold and 6 parts alloy metals, making it 75% pure. The word derives from the Arabic 'qirat,' a carob seed historically used as a counterweight for precious metals.
For everyday rings and bracelets subject to regular abrasion, 18K (75% gold) offers the best balance of durability and gold content. 22K is too soft for intricate stone settings and scratches more easily, though it remains popular in Gulf and Indian markets where the deep yellow color and high purity are culturally prized. 14K is excellent for active-lifestyle jewelry in the US and Eastern Europe.
Yes, using a nitric acid test kit available for under $30. You make a small scratch on the piece, apply acid matched to different karat levels, and observe the reaction: gold will not react while base metals dissolve. XRF (X-ray fluorescence) guns provide non-destructive, highly accurate testing but cost several thousand dollars — typically only available from dealers and assay labs.
Pure gold has a Vickers hardness of approximately 25 HV — softer than most metals. A 24K ring will scratch, dent, and lose its shape quickly under normal daily wear. Alloying gold with copper, silver, palladium, or zinc dramatically increases hardness: 18K alloys typically reach 120–180 HV depending on the alloy composition. 24K remains ideal for coins, bars, and investment pieces that are not subjected to physical stress.
'750' is the European fineness mark for 18-karat gold — it means 750 parts per 1,000 are pure gold (75%). European assay offices stamp fineness (per-thousand) rather than karat notation because it is unambiguous across languages. Other common fineness marks: 999 or 999.9 (24K), 916 or 917 (22K), 875 (21K), 585 (14K), 375 (9K).
Multiply the piece's weight in grams by the current gold spot price per gram (available on Serafa), then multiply by the purity factor of the karat: 24K = 1.000, 22K = 0.9167, 21K = 0.8750, 18K = 0.7500, 14K = 0.5833. Example: a 10-gram 18K bracelet with gold at $90/gram = 10 × $90 × 0.75 = $675 intrinsic (melt) value. Note that resale prices are typically 60–80% of this figure.
Editorial Standards: Content on this page is written and reviewed by the Serafa Editorial Team. We follow a strict fact-checking process and cite primary sources including the London Bullion Market Association (LBMA), the World Gold Council, and official assay office publications. Last reviewed: May 9, 2026.