Understanding Gold Purity: Karats, Fineness & How to Test Gold

What Is the Purity of Gold Called?

The purity of gold is most commonly expressed as its karat rating (not to be confused with “carat,” which measures gemstone weight). Karats run on a scale from 1 to 24, with 24 karats representing 100% pure gold. The more precise, internationally used technical term for gold purity is fineness — covered in detail below.

Gold Fineness Explained

While “karat” is the everyday term most people use, fineness is the more precise, globally standardized way of expressing gold purity, used especially in bullion, refining, and international trade.

Fineness is expressed as parts per thousand of pure gold in an alloy — so 24K gold at 99.9% pure is written as .999 fine, and ultra-high-purity gold at 99.99% is written as .9999 fine (often called “four nines” gold, common in investment-grade bars and coins).

Fineness and karat purity are two ways of describing the exact same thing:

This is also exactly where hallmark stamps come from. A “916” stamp on a ring is its fineness (91.6%) rounded to a three-digit code, and the same goes for “750” or “585” — the hallmark is simply the fineness figure stamped directly onto the metal, letting a jeweler or buyer verify purity at a glance without lab equipment. Refiners and bullion dealers almost always use fineness rather than karats when certifying bars and coins, since it’s a more exact, universally understood figure than the karat scale.

Gold Purity Chart: 24K, 22K, 21K, 18K & 14K Compared

24K Gold Purity Percentage: The Pinnacle of Purity

24K gold is the purest form available, containing 99.9% or more pure gold — often called “fine gold,” with negligible alloyed metal. Some 24K gold is refined to 99.99% purity (four nines) for high-value bullion or specific industrial uses. Its rich, vibrant yellow color and unmatched luster come from having essentially no alloy diluting the metal.

Because pure gold is extremely soft and prone to scratching or bending, 24K is the standard for bullion bars and coins (like the Canadian Gold Maple Leaf) and culturally significant jewelry in South Asia and the Middle East, but it’s impractical for daily-wear jewelry.

22 Carat Gold Purity Percentage — and What “916 Gold” Means

22K gold contains 91.67% pure gold, with 8.33% alloyed metals like copper, silver, or zinc added for extra durability while keeping purity high. This is where the 916 gold purity stamp comes from: 91.6% rounds to the “916” hallmark commonly used across India, the Middle East, and much of Asia to mark 22-karat gold.

So to directly answer a common question — is 916 gold considered 22K or 24K? — 916 gold is 22K, not 24K. It’s a popular standard for traditional bridal jewelry, bangles, and some gold coins like the Indian Sovereign, striking a balance between the value of high purity and the practicality of slightly added strength.

21 Carat Gold Purity Percentage

21K gold sits between 22K and 18K, containing 87.5% pure gold with 12.5% alloyed metal, hallmarked as “875.” It’s a purity level especially popular in Middle Eastern and some South Asian jewelry markets, offering a warm, rich yellow tone with slightly better scratch resistance than 22K, while still retaining a high, culturally preferred gold content.

18 Carat Gold Purity Percentage: The Jewelry Standard

18K gold contains 75% pure gold and 25% alloyed metal — commonly copper, silver, nickel, or zinc — hallmarked “750.” This higher alloy content unlocks a wider color range: copper produces rose gold, while nickel or palladium creates white gold.

18K is significantly more durable than 22K or 24K, making it the go-to purity for engagement rings, watches, and fine jewelry designed for daily wear, while still retaining strong intrinsic gold value.

14 Carat Gold Purity Percentage — and What Does 585 Purity Gold Mean?

14K gold contains 58.33% pure gold and 41.67% alloyed metal, the least pure of the commonly used karat levels, hallmarked “585.” So to directly answer it: 585 purity gold means 14-karat gold — 58.5% pure gold content, rounded from 58.33%.

The high alloy content makes 14K the hardest and most scratch-resistant of the common karats, and its lower gold content makes it the most affordable — a popular choice for wedding bands, everyday jewelry, and children’s pieces that need to withstand rough handling.

Gold Purity Color Chart

Purity alone doesn’t fully determine color — the type of alloy metal matters just as much:

• 24K–22K (high purity): Rich, deep yellow with almost no color variation, since there’s little alloy present to shift the tone.
• 21K: Warm yellow, slightly less intense than 22K.
• 18K: Available in yellow (traditional alloy mix), rose (copper-heavy alloy), and white (nickel or palladium alloy).
• 14K: Also available in yellow, rose, and white, but generally less vibrant than 18K in every color due to the higher proportion of alloy metal diluting the tone.

How to Test Gold at Home

If you’re trying to verify whether a piece of gold is genuine — or roughly confirm its karat — a few methods offer reasonable at-home checks, though none are a substitute for professional testing when real money is on the line.

Check the hallmark first. Nearly all legitimate gold jewelry and bullion carries a stamped purity mark — 999, 916, 875, 750, or 585 — usually on the inside of a ring band, the clasp of a chain, or the surface of a bar or coin. A missing or illegible hallmark on jewelry claiming high purity is an early warning sign, though counterfeiters can fake stamps too, so this alone isn’t proof.

The magnet test. Gold is not magnetic, so a strong magnet is a cheap, quick first check — if a piece is strongly attracted to a magnet, it’s not solid gold (though this only rules out some fakes, since many counterfeits use non-magnetic base metals too).

The float test. Pure gold is dense and will sink quickly in water rather than float or hover. Drop the piece into a glass of water: gold-plated fakes and hollow pieces often float or sink slowly, while genuine solid gold sinks fast and stays at the bottom.

The ceramic/unglazed tile scratch test. Gently scratch the piece against an unglazed ceramic surface. Real gold leaves a gold-colored streak; base metals or gold-plated items typically leave a black or grey streak instead. This test does scratch the item slightly, so it’s best used on a discreet spot.

The nitric acid test. Jewelers commonly use nitric acid test kits, applying a drop of acid to a small scratch in the metal. Pure or high-karat gold shows little to no reaction, while lower-karat gold or base metal reacts visibly (fizzing, color change, or dissolving).

This method is accurate for spot-checking karat range but requires handling a mild acid safely, and it isn’t something most people should attempt without a proper kit and ventilation.

Professional XRF testing. For anything valuable — bullion purchases, inherited jewelry, or high-value pieces — the gold standard (literally) is X-ray fluorescence (XRF) testing, a non-destructive method jewelers and refiners use to determine exact purity in seconds without damaging the item.

If you’re making a significant purchase or need a certified purity reading, a professional XRF test or an independent assay is the only fully reliable option — home tests are useful for a quick sanity check, not a final verdict.

Factors to Consider When Choosing Gold Purity

• Purpose: For investment, 24K gold is ideal for its high purity and value retention. For jewelry meant to be worn daily, 18K or 14K offers far better durability.
• Budget: Higher-karat gold costs more per gram due to its higher gold content; 14K offers the most budget-friendly entry point.
• Aesthetics: Higher-karat golds show a richer, more intense yellow; 18K and 14K offer more color variety (yellow, white, rose).
• Allergies: Those with sensitive skin often do better with 24K or 22K gold, or 18K/14K pieces specifically alloyed with hypoallergenic metals like palladium rather than nickel.
• Durability needs: For rings, bracelets, or anything worn daily, 18K or 14K’s added hardness matters more than maximum purity.

Frequently Asked Questions About Gold Purity

What is the purity of gold called?
Gold purity is measured in karats (the common consumer term) or fineness (the precise technical measurement, expressed as parts per thousand, such as .999 or .9999).

Is 916 gold considered 22K or 24K?
916 gold is 22K gold — the “916” hallmark refers to 91.6% purity, which is the standard fineness for 22-karat gold.

What does 585 purity gold mean?
585 purity gold means 14-karat gold — a 58.5% gold content hallmark, commonly used across Europe and internationally to mark 14K pieces.

The Bottom Line

Understanding the difference between 24K, 22K, 21K, 18K, and 14K gold — recognizing hallmark stamps like 916, 875, 750, and 585, and knowing the basics of how to test gold’s authenticity — helps you make informed decisions whether you’re buying jewelry, investing in bullion, or simply trying to understand what’s stamped on a piece you already own.

Higher purity means higher intrinsic value but lower durability; lower purity trades some value for everyday practicality. For anything beyond casual curiosity, a professional purity test is always worth the small cost before a significant purchase or sale.