Gold Karat Calculator
Compare how karat purity changes the value of the same gold weight.
What karat actually measures
Karat is a purity fraction with 24 as the denominator. An 18K item contains 18 parts gold to 6 parts other metal by weight, which is 75% gold. 14K is 14 parts in 24, or 58.33%. 10K is 41.67%, the legal minimum that can be sold as gold in the United States. Pure gold is alloyed for two reasons. Hardness: 24K gold can be scratched with a fingernail and deforms under normal wear, so a 24K ring worn daily loses its shape and detail. And colour and cost: copper pushes gold pink, silver and zinc pale, and nickel or palladium plus rhodium plating produce white gold. So karat is a trade-off, not a quality ranking. A 10K ring is more durable and holds a stone setting better. A 22K bangle carries more value per gram and resells closer to spot. Neither is the right answer in the abstract.
Value per gram at every karat
Holding spot at $4,060 per troy ounce so the comparison is clean, one gram of pure gold is $130.53. Scaled by karat decimal: 24K (0.999) = $130.40 per gram. 23K (0.958) = $125.05. 22K (0.9167) = $119.66. 21K (0.875) = $114.21. 20K (0.833) = $108.73. 18K (0.750) = $97.90. 16K (0.667) = $87.06. 14K (0.5833) = $76.14. 12K (0.500) = $65.27. 10K (0.4167) = $54.39. 9K (0.375) = $48.95. 8K (0.333) = $43.47. The spread is bigger than most people expect: a gram of 22K carries 2.20 times the gold value of a gram of 10K. Enter the same weight and change only the purity to see this directly.
Why heavier low-karat often beats lighter high-karat
Because value is weight multiplied by purity, a big 10K piece can easily contain more gold than a small 18K piece. A 40 gram 10K curb chain holds 16.7 grams of fine gold; a 12 gram 18K pendant holds 9 grams. The chain is worth roughly 85% more despite being "lower quality" gold. This catches people out in both directions. Sellers overvalue small high-karat items and undervalue heavy chunky low-karat ones, and secondhand buyers sometimes pay a premium for an 18K stamp on a piece that is mostly air. The fix is to compute fine gold weight - grams times karat decimal - and compare that number across items. It is the only figure that maps directly to money.
Reading karat and fineness stamps
Most of the world stamps millesimal fineness rather than karat, and the two notations say the same thing. The pairs: 999 is 24K, 958 is 23K, 916 is 22K, 875 is 21K, 833 is 20K, 750 is 18K, 667 is 16K, 585 is 14K, 500 is 12K, 417 is 10K, 375 is 9K and 333 is 8K. Older US 14K jewelry is sometimes stamped 583 rather than 585. That is not a defect - it reflects the legal half-karat tolerance permitted on unplumbed gold. A piece marked 14KP or "14K plumb" is guaranteed a full 14K with no tolerance applied. Marks that are not solid gold: GP and GEP (gold plated), HGE (heavy gold electroplate), RGP (rolled gold plate), GF and fractional forms like 1/20 12K GF (gold filled), and vermeil (gold over sterling). A trap worth naming: "18KGP" is plated - the GP governs, and the 18K describes the plating alloy rather than the item.
Where each karat is used
24K appears almost exclusively as bullion - bars, Maple Leafs, Buffalos, Britannias, Pandas, Philharmonics - and as jewelry in parts of East and Southeast Asia, where jewelry doubles as savings and resale value matters more than wearability. 22K (916) is the South Asian jewelry standard and the alloy of the Krugerrand and American Gold Eagle. 21K (875) dominates Gulf markets. 23K (958) is common in Thai jewelry. 18K (750) is the European fine jewelry standard and the default for luxury watches and designer work. 14K (585) is the workhorse of the US market and by far the most common karat in American scrap lots. 10K (417) is US budget jewelry, class rings and mass-market chain. 9K (375) is the UK and Australian equivalent and cannot legally be sold as gold in the US. Knowing the regional norm helps with unmarked pieces: a heavy yellow bangle bought in Dubai is probably 21K; the same shape from a US mall is probably 10K or 14K.
Karat, durability and resale
On hardness, 14K yellow typically lands around 130-150 HV and 18K yellow around 120-135 HV, so 14K is meaningfully more scratch-resistant. For daily-wear rings that matters: 18K shows wear and rounded-over detail faster, and 14K prongs hold stones more securely over years. For earrings, pendants and occasional-wear pieces the difference is largely irrelevant. In white gold the relationship inverts usefully. 14K white starts whiter because there is more white alloy in it, so when rhodium plating wears - and it always does - 14K white shows less yellow underneath. On resale, higher karat sells closer to spot as metal, because refiners prefer high-purity simple alloys with less processing cost per gram recovered. But as jewelry, karat matters far less than brand, condition and design. An 18K unbranded hollow chain will not hold value the way a 14K piece from a recognised maker does.
Is 22K always worth more than 18K?
Per gram, yes - 22K contains 91.7% fine gold against 18K's 75%, so a 22K gram is worth about 22% more. But a heavier 18K item can easily be worth more overall, because total value is weight multiplied by purity. Always compare fine gold weight rather than karat alone.
What if my item is not stamped?
An absent stamp is weak evidence either way, since marks wear off, get polished away during repair, and were never applied to many handmade and antique pieces. Test rather than guess: density is the best free check, and XRF at a dealer gives a definitive alloy breakdown in seconds without damaging the piece.
Does colour affect karat value?
No. Yellow, white and rose gold can all be the same karat with different alloy metals - copper for rose, nickel or palladium for white. Colour tells you about the alloy, not the purity. Only the hallmark or a test tells you the karat.
What does 585 mean on my jewelry?
585 is a millesimal fineness mark meaning 58.5% gold, which is 14K. The common marks are 999 for 24K, 916 for 22K, 875 for 21K, 750 for 18K, 585 for 14K, 417 for 10K and 375 for 9K.
Which karat is best for an engagement ring?
14K is generally the better choice for a daily-wear ring: it is harder, more scratch-resistant, and holds prong settings more securely over years. 18K gives a richer yellow and higher gold content, and is a better fit for pieces that do not take constant abrasion. For sensitive skin, higher karat means less alloy and so less of whatever the irritant is - though specifying nickel-free or palladium white gold matters more than the karat number.
Can I compare several karats at once?
Yes. Enter the same weight and change only the purity option to see how much fine gold each karat contains at that weight. For a real mixed lot, use multiple-item mode so each piece keeps its own karat.