How Gold Price Per Gram Is Calculated
The full method: troy ounce to gram, karat purity to decimal, and the three mistakes that throw estimates off by 10-40%.
Updated July 29, 2026
The two-step formula
Every gold price per gram figure you will ever see comes from the same two steps. First you convert the market price, which is quoted per troy ounce, into a price per gram of pure gold. Then you scale that down by the purity of the specific item you are holding. Step one: divide the spot price per troy ounce by 31.1035. A troy ounce contains exactly 31.1034768 grams, and 31.1035 is the rounding every refiner and dealer uses. If gold is trading at $4,060 per troy ounce, a gram of pure 24K gold is $4,060 ÷ 31.1035 = $130.53. Step two: multiply by the karat decimal. Karat is a fraction of 24, so divide the karat number by 24 to get the decimal. An 18K item is 18 ÷ 24 = 0.750, so a gram of 18K gold contains $130.53 × 0.750 = $97.90 of gold. A 14K gram at the same spot price is $130.53 × 0.5833 = $76.14. That is the entire calculation. Everything else - currencies, pennyweights, tolas, multi-item lots - is unit conversion layered on top of these two steps.
Worked example: a 14K chain
Say you have a 14K gold chain that weighs 18.4 grams, and the live spot price is $4,060 per troy ounce. Convert weight to troy ounces: 18.4 ÷ 31.1035 = 0.5916 troy ounces gross. Apply purity: 14K is 58.33% gold, so 0.5916 × 0.5833 = 0.3451 troy ounces of fine gold. Multiply by spot: 0.3451 × $4,060 = $1,401. You can run the same numbers per-gram instead and land in the same place: 18.4 g × $76.14 per 14K gram = $1,401. Use whichever order is easier to check in your head. That $1,401 is the melt value - the market value of the recoverable gold. A specialist buyer paying 85% of melt would offer around $1,191. A pawn shop paying 55% would offer around $771. Same chain, same spot price, a $420 spread that depends entirely on which door you walk through.
Karat to decimal reference
Karat stamps and millesimal fineness stamps describe the same thing in different notation. A 750 stamp and an 18K stamp are identical claims. These are the multipliers to use in the formula: 24K = 999 fine = 0.999 multiplier. 23K = 958 = 0.958. 22K = 916 = 0.9167. 21K = 875 = 0.875. 18K = 750 = 0.750. 14K = 585 = 0.5833. 10K = 417 = 0.4167. 9K = 375 = 0.375. 8K = 333 = 0.3333. Two conventions worth knowing. US law allows a half-karat tolerance on unplumbed gold, so a piece stamped 14K may assay at 13.5K; older US 14K jewelry is sometimes stamped 583 rather than 585 for exactly this reason. And 24K is treated as 0.999 rather than 1.000 in practice because commercially refined gold is 99.9% fine, not chemically perfect.
The three mistakes that ruin estimates
Mistake one: the wrong ounce. A troy ounce is 31.1035 grams. The avoirdupois ounce on a kitchen or postal scale is 28.3495 grams. Divide by 28.3495 instead of 31.1035 and every number you produce is 9.7% too high. This is by far the most common error, and it is the reason a lot of people feel low-balled by an honest buyer. Mistake two: gross weight treated as gold weight. Buyers pay for recoverable gold. Gemstones, glass, enamel, watch movements, steel spring bars, clasp mechanisms and non-gold pins all weigh something and contain no gold. A ring with a 1-carat centre stone can carry 0.3-0.5 grams of non-gold weight, and hollow rope chains can be dramatically lighter than their appearance suggests. Mistake three: trusting the stamp on plated goods. GP (gold plated), GF (gold filled), HGE (heavy gold electroplate), RGP (rolled gold plate) and vermeil are surface treatments over brass or silver. Gold filled is typically 5% gold by weight and is technically refinable, but most buyers will not take it. Anything marked GP or HGE has effectively no melt value regardless of how heavy it feels.
Working in other units
Pennyweight (dwt) is the unit most US jewelers and pawn shops quote in, and the switch trips people up because a dwt price looks smaller than a gram price when it is actually larger. One dwt is 1.5552 grams, and 20 dwt make a troy ounce. To get a dwt price, divide the troy ounce price by 20: $4,060 ÷ 20 = $203 per dwt of pure gold, or $118.42 per dwt of 14K. Tola is standard across India, Pakistan and Bangladesh at 11.6638 grams, so a tola of 22K gold at $4,060 spot is 11.6638 × $130.53 × 0.9167 = $1,395. The Thai baht unit is 15.244 grams for jewelry and is conventionally quoted on 96.5% gold. Grams are the safest unit to compare offers in, because everything converts cleanly and there is no ambiguity. If a buyer quotes per pennyweight and another quotes per gram, convert both to grams before you compare - the difference is 55.5%, which is more than enough to hide a bad offer inside.
Why the number moves while you watch it
Gold trades nearly around the clock, roughly 23 hours a day across Sunday evening to Friday afternoon US time, so the spot price shifts continuously. A 1% intraday move on a $4,000 ounce is $40, which is $1.29 per gram of pure gold. On a 50-gram lot that is a $64 swing between morning and afternoon. If you are not pricing in US dollars there is a second moving part. Gold is quoted in USD, so your local price is the USD price multiplied by an exchange rate. Your currency can move against the dollar even when gold itself is flat, and both can move at once in the same or opposite directions. This is what the manual price field is for. If a dealer quoted you a price at 10am and you want to check their arithmetic, type their spot price in rather than using the live feed - otherwise you are comparing their quote against a different market than the one they quoted from.
What the per-gram number does and does not tell you
A per-gram melt figure answers exactly one question well: is the offer in front of me in the right neighbourhood? It is a benchmark for negotiation and a filter for obviously bad offers. It is not a prediction of what you will be paid. It also says nothing about the non-metal value of an item. A signed Cartier or Van Cleef piece, an antique with provenance, a hallmarked Victorian mourning brooch or a designer watch case can be worth several multiples of melt on the secondhand market. If a piece has a maker mark you recognise, get it appraised as jewelry before you sell it as scrap - melting is irreversible. For plain scrap - broken chains, single earrings, bent rings, dental gold - melt value is the right frame, and knowing it to within a few percent puts you in a far stronger position than walking in cold.
Key points
Price per gram of pure gold = spot price per troy ounce ÷ 31.1035. Multiply that by the karat decimal (24K = 1.000, 18K = 0.750, 14K = 0.583, 10K = 0.417). Using a kitchen ounce instead of a troy ounce inflates the result by about 9.6%. The result is melt value, which is the ceiling on any offer, not the offer itself.