GoldToPrice guide · Updated 2026-10-11
Gold Karat and Purity Explained: 9K, 14K, 18K & 24K
Karat is the gold fraction on a 24-part scale. Fineness marks express gold content per thousand parts, so 750 means 75% gold and 375 means 37.5%.
Two systems describe the same gold content
Karat, commonly written K or kt in American jewelry and ct in Britain, divides an alloy into twenty-four parts. Eighteen-karat gold contains eighteen parts gold in twenty-four, or 75% by mass. A millesimal fineness mark expresses that proportion in thousandths: 750. The remaining material is not empty space; it consists of alloy metals used to alter strength, color and working properties. The karat number is not the same as a gemstone carat, which measures weight. Both words appear in jewelry listings, making confusion easy. A ring described as 18K with a one-carat diamond has a gold purity and a separate gemstone weight. Start by identifying which measurement a seller is quoting. Neither the gemstone weight nor the retail price tells you the ring's net gold-bearing metal weight.
Read nominal karat and stamped fineness carefully
Some familiar fineness marks are slightly different from the exact karat fraction. Fourteen divided by twenty-four is about 0.583333, while a 585 mark describes 0.585. Twenty-two divided by twenty-four is about 0.916667, while a 916 stamp describes 0.916. Ten-karat gold is about 0.416667 and may carry a 417 mark. Our karat tables use disclosed nominal factors, rounded to four decimal places, except the 24K estimate uses 0.999. If you have a reliable assay showing a precise fineness, use that figure for a formal settlement rather than treating the website's nominal factor as a laboratory result. The difference is small but real, and can become noticeable on a large lot. A buyer should explain whether its quote uses the karat label, the stamp or an actual assay.
Compare 9K and 10K without treating them as fake
Nine-karat gold contains 37.5% gold and is associated with 375 fineness. Ten-karat gold contains approximately 41.67% gold. Both have substantial non-gold alloy content, so they generally have a lower fine-gold value per gram than 14K or 18K pieces of equal net weight. That does not make a correctly described solid low-karat item gold-plated. Its alloy contains gold throughout, whereas plating is a surface layer. Local marking rules matter: Britain recognizes 375 as a gold hallmarking standard, while American jewelry descriptions operate under FTC guidance and must accurately disclose fineness and construction. Do not infer a universal legal minimum from a familiar retail convention. Low-karat alloys can respond differently to wear, chemicals or skin contact depending on their composition, not simply their number.
Why 14K and 18K are different purchases
Fourteen-karat and eighteen-karat jewelry often serve the same everyday uses, but their metal content differs. For equal net weight, 18K has more fine gold: 75% rather than about 58.33%. That increases the melt reference but does not automatically make the finished piece stronger or better designed. Hardness depends on the alloy recipe and manufacturing as well as purity. White, yellow and rose gold can all be 18K, and their colors are not a reliable assay. White gold may have a surface finish that changes its appearance over time. When comparing rings, look at dimensions, construction, stone setting, repairability and the metal allergy information as well as the karat. A delicate high-priced design can contain less gold than a heavier lower-karat band.
High-purity jewelry and bullion have different conventions
Twenty-one-karat gold is 87.5% fine and is associated with 875 marks. Twenty-two-karat gold is approximately 91.67% fine and is widely encountered in South Asian and Middle Eastern jewelry. These are useful regional clues, not a guarantee about every item sold in a country. Pure-gold products commonly use 999 or 9999 fineness. In everyday descriptions these may be called 24K, but a specific stamped number is more precise than that category label. Investment coins also require special care. An alloyed coin can be specified to contain a full troy ounce of fine gold even though its total weight is greater than one ounce. For that coin, use the mint's stated fine-gold content; multiplying a one-ounce fine-content label by its karat again would undervalue it.
Turn purity into fine-gold weight
First identify the net metal weight after excluding stones and components that are not part of the tested gold alloy. Multiply that weight by the purity fraction. A hypothetical 8 g piece at 750 contains 8 × 0.75 = 6 g of fine gold. A 12 g piece at 375 contains 4.5 g. Only then multiply fine-gold grams by the spot price per gram. The examples are measurements for illustration, not a claim about your jewelry. If you have several karats, calculate each group independently and add the fine-gold weights or values. Combining all weights and using a simple average karat loses the relationship between weight and purity. The mixed scrap calculator and the individual karat pages make that separation visible.
Recognize construction marks that change the formula
Marks such as GP, GF, RGP and HGE refer to forms of coating or bonded gold layer, not a solid alloy of the stated karat throughout the item. A marking that includes 14K GF does not mean the full gross weight should be valued as solid 14K. Gold-filled construction can contain a meaningful gold layer, but recovery depends on the layer specification, substrate and buyer's refining process. Plated pieces may have very little recoverable value relative to the cost of handling them. Do not apply a solid-gold multiplier just because a gold-colored item has a K number somewhere on it. Inspect the complete mark and ask a professional if it is unclear. Similarly, vermeil describes a gold coating over silver; the underlying silver may be the more relevant metal reference.
Use purity to compare offers, not to appraise design
A karat table helps compare the metal part of an offer. It does not price gemstones, craftsmanship, brand demand or the cost of replacing a finished item. When buying, a premium above melt can be entirely normal; ask what you are paying for and whether it matters to you. When selling, confirm whether the buyer is considering resale or only scrap. Preserve items with potential second-hand or collector value until that choice is clear. For a dispute about purity, a visual stamp or a calculator is not enough; seek appropriate testing and a documented result. Our methodology explains the nominal factors and the feed timestamp so you can reproduce the math. Keep those assumptions separate from any assay certificate, local hallmark guarantee or formal appraisal that applies to the actual object.
Put the explanation into today's numbers
Gold · USD · per troy ounce · spot value
$4,186.10
-0.20% over 24h
Last quote
With the current reference, fine gold is $134.59 per gram. An illustrative 10 g 18K item has a melt value of $1,009.40; a hypothetical 80% buyer payout is $807.52. The payout is an assumption, not an observed offer.
Frequently Asked Questions
Does 585 mean exactly the same as nominal 14K?+
585 means 58.5% gold, while 14 divided by 24 is approximately 58.333%. A precise settlement should use the applicable tested or stamped fineness.
Is 18K white gold less pure than yellow gold?+
No. The same karat describes the same nominal gold fraction; the alloy mix and surface finish affect color.
Do I multiply a coin's fine-gold ounce by its karat?+
No. If a mint already states the fine-gold content, use that content directly rather than applying purity a second time.
Sources & editorial note
GoldToPrice publishes this educational reference. No individual expert credential or independent review is claimed. Calculations use our disclosed data methodology; official rules and product terms take precedence. Report corrections at hello@metalflowapi.com.