Gold & Silver
Understanding Gold Purity: 24K, 22K, 18K Explained
Reviewed by Thomas & Øyvind — NorwegianSpark | Last updated: April 2026
The Karat System: A Quick History
The karat system dates back centuries and divides gold purity into 24 parts. Pure gold is 24 karat, meaning all 24 parts are gold. An 18 karat piece contains 18 parts gold and 6 parts other metals. The word karat itself derives from the carob seed, which ancient merchants used as a counterweight on balance scales due to its remarkably consistent weight.
Today the karat system remains the global standard for expressing gold purity in jewellery and coinage. Investment-grade bullion more commonly uses the fineness system, expressed in parts per thousand. Both systems convey the same information: 24 karat equals 999.9 fine, 22 karat equals 916.7 fine, and 18 karat equals 750 fine. Understanding both notations helps you navigate the gold market with confidence.
24 Karat Gold: The Purest Form
At 99.99 percent purity, 24 karat gold is as close to pure elemental gold as modern refining can achieve. It has a distinctive deep yellow colour and is extremely soft and malleable. This softness makes it impractical for most jewellery applications but ideal for investment bullion, where the goal is to own the maximum amount of pure metal per unit of weight.
Premium investment products such as PAMP Suisse bars, the Canadian Gold Maple Leaf and the Austrian Gold Philharmonic are all struck at 24 karat. Their high purity qualifies them as investment gold under European VAT regulations, exempting them from value-added tax in most EU and EEA countries. For investors, 24K gold offers the simplest valuation: multiply the weight by the spot price and you know exactly what the metal is worth.
22 Karat Gold: Durability Meets Tradition
The American Gold Eagle, South African Krugerrand and British Gold Sovereign are all minted at 22 karat, containing 91.67 percent gold with the balance in copper and silver. This alloy is significantly harder than pure gold, resisting scratches and wear that would quickly mar a 24K surface. The slightly reddish hue of the Krugerrand, for example, comes from its copper content.
Importantly, these coins still contain a full troy ounce of pure gold. The total coin weight is simply higher than one ounce to account for the alloy metals. Pricing is based on gold content, not total weight, so a one-ounce Eagle and a one-ounce Maple Leaf contain the same amount of gold despite different total weights. This makes 22K coins fully interchangeable with 24K products for investment purposes.
18 Karat and Below: The Jewellery Standard
Eighteen karat gold, at 75 percent purity, is the international standard for fine jewellery. It strikes a practical balance between the warm colour of gold and the hardness needed for everyday wear. The remaining 25 percent alloy can be configured to produce different colours: copper creates rose gold, palladium or nickel produces white gold, and silver enhances yellow tones.
Below 18K, you enter the territory of 14K (58.3 percent) and 10K (41.7 percent), which are common in the United States and some Northern European markets. While these purities are durable and affordable, they contain less actual gold per gram and generally do not qualify for investment-gold tax exemptions. If you are buying jewellery as both an adornment and a store of value, 18K from reputable brands offers the best balance.
How Purity Affects Investment Value
For bullion investors, purity directly determines the intrinsic metal value. A 100-gram bar at 999.9 fineness contains 99.99 grams of pure gold, while a 100-gram bar at 916.7 fineness contains only 91.67 grams. When comparing products, always calculate the price per gram of pure gold content rather than the price per gram of total weight. This apples-to-apples comparison reveals the true cost of your investment.
Liquidity is also affected by purity. Products from LBMA-accredited refiners at 999.5 fineness or above are accepted worldwide without assay, meaning they can be traded on the international wholesale market. Lower-purity items may require re-assaying before sale, adding cost and delay. For maximum liquidity and universality, stick to 24K or 22K products from internationally recognised mints and refiners.
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Frequently Asked Questions
What does 999.9 fine gold mean?
The fineness system measures gold purity in parts per thousand. A marking of 999.9 means the gold is 99.99 percent pure, which is the highest standard commercially available. This is sometimes called four-nines fine and is the standard for investment-grade bars from refiners like PAMP Suisse, Valcambi and the Royal Canadian Mint. Most gold bullion coins are minted at 999.9 or 999.0 fineness, making them suitable for VAT-exempt investment gold in many European jurisdictions.
Why are some gold coins only 22 karat?
Coins like the American Gold Eagle and South African Krugerrand are minted at 22 karat (91.67 percent gold) because the remaining alloy of copper and silver makes them significantly more durable and scratch-resistant. Despite being 22K, these coins still contain a full troy ounce of pure gold; the coin simply weighs slightly more than an ounce to compensate for the alloy content. This durability made them the standard for circulating gold coins throughout history.
Does higher karat gold always command a higher price?
For investment bullion, the price is based on the pure gold content, so a 22K one-ounce coin and a 24K one-ounce coin containing the same amount of pure gold should trade at similar prices. However, premiums can vary based on the coin's popularity, mintage and brand recognition. In the jewellery market, 18K pieces can command significant premiums due to craftsmanship, design and brand value, but this is unrelated to the metal content alone.