18K Gold Calculator

18K: three-quarters pure

18K gold is 75% pure — 18 of 24 parts gold. It is the karat of choice for European jewelry houses and high-end American designers, prized for its richer color and the prestige of higher gold content. Luxury watch cases, designer engagement rings, and most fine jewelry made in Italy or France are 18K gold. To compare offers across a whole jewelry box, start with the scrap gold calculator — this page is the same engine with the purity preset to 18 karat.

Purity explains the price ladder at a glance: 18K gold carries roughly 80% more gold per gram than 10K and about 29% more than 14K, while giving up a little of the hardness lower alloys offer. That is the whole trade — more gold, softer metal, higher melt value — and it is why an 18K piece deserves a careful weighing even when it looks too small to matter.

How to calculate 18K gold value per gram

Divide the current spot price per troy ounce by 31.1035 to get the pure-gold price per gram, then multiply by 0.75. That is your 18K price per gram; multiply by weight for the melt value. Because 18K carries 75% gold, a modest 5-gram ring holds meaningfully more metal value than the same ring in 14K.

Per-gram framing also helps when quotes arrive in odd units. Divide any per-troy-ounce offer by 31.1035 and any per-pennyweight offer by 1.5552 to reach a per-gram figure, then compare it with the 18K per-gram value shown above. Buyers count on unit friction; one division removes it, and it works for any karat of gold, not just 18K.

Worked example: a 6-gram 18K designer ring

Set the spot price at $4,000 per troy ounce for illustration. Pure gold is $4,000 ÷ 31.1035 = $128.60 per gram; 18K gold is $128.60 × 0.75 = $96.45 per gram. A 6-gram gold ring therefore melts at about $579. The payout tiers turn that into offers: a pawn shop at 55–70% pays roughly $318–$405, a local jeweler at 70–85% about $405–$492, an online gold buyer at 80–95% around $463–$550, and a refiner at 95–98% up to $550–$567.

Notice how wide the money gap runs at 18K: the same ring fetches $318 at the worst counter and $567 at the best, a $249 spread on a single item. Higher purity amplifies every percentage point, which is why a second quote matters more for 18K than for any lower karat.

What the 750 stamp means on gold jewelry

European and most designer 18K pieces are stamped "750" rather than "18K" — millesimal fineness, meaning 750 parts gold per thousand. Both marks describe identical purity. You may also see "18KT" or, on older pieces, a maker's hallmark next to the fineness mark. If a piece is stamped 750, run it through this calculator at 18 karat.

Beyond the 750, European pieces often carry a maker's mark and an assay office mark alongside the fineness number. Those extra hallmarks are good news: they make provenance easier to establish and give a resale-minded buyer a reason to pay above scrap. Photograph all marks before selling anything; once a piece is melted, the evidence is gone.

18K vs. 14K: the trade-off

Gram for gram, 18K is worth about 29% more than 14K because of the extra gold content. The trade-off runs the other way in durability: 18K is softer and scratches more easily, which is why everyday American rings default to 14K. For sellers the takeaway is simple — 18K is where scrap gold value adds up fastest, so double-check stamps before assuming a fancy-looking piece is only 14K. And if a stamp turns out to read 585 rather than 750, switch to the 14k gold calculator so the purity matches the mark.

When you sell, the usual payout ladder applies: 55–98% of melt depending on whether you are dealing with a pawn shop, a local jeweler, an online buyer, or a refiner. One caution specific to 18K: because these pieces are often from designer houses, some carry resale value above melt — a signed Cartier or Tiffany item can be worth far more intact than melted. Check the maker's marks before treating any 18K piece as scrap.

Plated marks that imitate 18K gold

"18K GP", "18K HGE", and "18KGP" stamps appear constantly on fashion jewelry, and none of them mean solid gold. GP is gold plated and HGE is heavy gold electroplate — in both cases a micron-scale layer of 18K over brass or steel, containing too little gold for most scrap buyers to bother recovering. A solid piece says 18K or 750 with no suffix; when in doubt, an acid test or a magnet check (solid gold is never magnetic) sorts it quickly.

Gold-filled 18K ("1/20 18K GF") is the middle case: a real bonded layer amounting to one-twentieth of the item's weight. Refiners buy gold-filled material in bulk, but a single gold-filled item is usually worth more as wearable jewelry than as scrap. Weigh gold-filled separately from solid gold if you send in a refiner lot; mixing the two invites the whole box to be settled at the lower recovery rate.

Where to sell 18K gold for the most money

The standard ladder — pawn shops at 55–70% of melt, local jewelers 70–85%, online buyers 80–95%, refiners 95–98% — applies to 18K gold, but two 18K-specific opportunities sit above it. First, signed designer pieces: a hallmarked Cartier, Tiffany, or Bulgari item usually resells intact for well above melt, so identify maker's marks before any scrap conversation. Second, watches: a solid 18K case is heavy, and a buyer quoting the whole watch "as scrap" may be ignoring a movement worth money on its own.

Weigh before you go — the gold calculator in grams explains why a 0.1 g pocket scale is worth its $10 price — and bring your own melt figure. At 75% purity, every gram miscounted and every percentage point conceded costs nearly twice what the same mistake costs on 10K.

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