Gold Weight Calculator

How the Gold Weight Calculator Works

Enter your item's weight, select its carat, and the calculator returns the pure gold content and an estimated scrap value. The formula behind every gold valuation in the trade is the same three-step multiplication:

A 20g chain hallmarked 9ct contains 20 × 0.375 = 7.5g of pure gold. At a spot price around £65 per gram, that is roughly £487.50 of pure gold content, though what a dealer actually pays sits below that (a distinction unpacked in the next sections). For calculating taxes on gold investment profits, check our Capital Gains Tax Calculator or general portfolio assets with our Portfolio Return Calculator.

Carats, Hallmarks and Purity Fractions

Carats measure purity out of 24, so the fraction of pure gold in an item is simply its carat divided by 24:

• 9ct: 37.5 percent gold, hallmarked 375
• 14ct: 58.5 percent gold, hallmarked 585
• 18ct: 75 percent gold, hallmarked 750
• 22ct: 91.6 percent gold, hallmarked 916
• 24ct: 99.9 percent gold, hallmarked 999

The three-digit hallmark stamped on UK gold is the purity in parts per thousand, applied by one of the UK's assay offices. It is legally required on most gold items sold in the UK above 1 gram. British jewellery is dominated by 9ct, which is why two similar-looking chains can differ in value by two and a half times: an 18ct piece carries exactly twice the gold of a 9ct piece of the same weight.

Troy Ounces: The Unit That Catches People Out

Gold markets price in troy ounces, and a troy ounce is not a normal ounce. One troy ounce equals 31.103 grams, against 28.35 grams for an everyday avoirdupois ounce—a 10 percent difference that has confused sellers for centuries. When a headline says gold is at a certain price per ounce, dividing by 31.103 gives the price per gram that all UK scrap and jewellery maths runs on.

For weighing at home, digital scales reading to 0.1g are accurate enough for an estimate. Two honesty adjustments matter before trusting the number: stones, clasps with steel springs, and solder are not gold and must be deducted from the payable weight. Second, gold-plated items (marked GP, GEP, or rolled gold) carry only a microscopic gold layer with essentially no scrap value.

From Gold Content to Actual Payout

The value the formula produces is the melt value of the gold content, and no buyer pays 100 percent of it. Reputable UK dealers typically pay somewhere between 70 and 95 percent of the gold content value, with higher purities and larger quantities earning better percentages because they are cheaper to refine.

That spread is exactly why the calculator matters: knowing your item holds £700 of gold turns a £400 offer from a lowball into a real negotiation. Sovereign and Britannia bullion coins follow a different route, priced on the coin market rather than as scrap, and UK legal tender gold coins carry the additional advantage of being exempt from Capital Gains Tax.

Practical Selling Tips

Get quotes from at least three buyers, ask whether the quoted rate is per gram of item weight or per gram of pure gold, and expect any serious buyer to verify purity with an XRF machine rather than acid alone.