Troy Ounce vs Gram vs Pennyweight
Three units, one metal, and one conversion mistake that regularly costs sellers real money.
If you have ever tried to sell gold, you have probably been quoted a price in a unit you did not expect. A pawnbroker talks in pennyweights. A news headline talks in ounces. Your kitchen scale talks in grams. A relative in Mumbai talks in tolas. They are all describing the same physical stuff, but the numbers look wildly different, and that difference is exactly where confusion — and occasional exploitation — lives. This guide untangles the three units you are most likely to meet in the English-speaking gold trade: the troy ounce, the gram, and the pennyweight.
The troy ounce: the unit gold is actually priced in
When you see "gold is trading at $4,686 an ounce," that ounce is a troy ounce, not the ounce you use for cooking. A troy ounce weighs 31.1035 grams. The everyday ounce — properly called the avoirdupois ounce — weighs only 28.3495 grams. The troy ounce is about 10% heavier, which matters enormously when you are multiplying by a four-figure price.
The troy system is ancient. It takes its name from the French market town of Troyes, a major medieval trading hub, and it survived into the modern era specifically for precious metals and gemstones because the bullion world never had a reason to abandon it. Today every serious gold quote on the planet — London, New York, Zurich, Shanghai — is denominated in US dollars per troy ounce. That is the number the whole market is anchored to.
One quirk worth remembering: a troy pound contains 12 troy ounces, not 16. The troy pound is essentially obsolete, but the "12 ounces to the pound" fact is a good reminder that troy weights are their own self-contained system and you cannot casually mix them with kitchen weights.
The gram: the unit you can actually measure
The gram is the workhorse of retail gold. Jewelers weigh pieces in grams, jewelry scales read in grams, and most of the world outside the United States thinks about gold per gram. It is a metric unit, universally understood, and easy to verify: any digital jewelry scale accurate to 0.01 g will do.
Because the market prices gold per troy ounce but you weigh it in grams, every melt-value calculation quietly performs one division: price per gram equals the spot price divided by 31.1035. At a spot price of $4,686, that is about $150.66 per gram of pure (24K) gold. From there you multiply by weight and by the purity of your karat. Our gold calculator does this automatically, but it is worth understanding the mechanism so a dealer cannot bluff you with the math.
The pennyweight: the unit that trips people up
The pennyweight, abbreviated DWT (the "d" is from the Latin denarius), is where first-time sellers lose money. One pennyweight equals 1.5552 grams, or exactly one-twentieth of a troy ounce (20 pennyweights make a troy ounce). It is a traditional unit of the North American jewelry and scrap trade, and many pawn shops and gold buyers still quote their buying prices per DWT.
There is nothing dishonest about the pennyweight itself. The problem is the mismatch between how a buyer weighs and how a seller thinks. Imagine you bring in a chain and the buyer says "I'll give you $90 a pennyweight." That sounds generous next to a per-gram figure — until you realize a pennyweight is 1.56 grams, so $90/DWT is really about $58 per gram. If you were mentally comparing it to a $95-per-gram melt value, you might think you were getting a great deal when you were actually being offered a steep discount.
The classic trap: a buyer weighs your gold in pennyweights but lets you assume the number on the scale is grams. Twelve grams of gold is only about 7.7 pennyweights. If the scale reads "7.7" and you think "7.7 grams," you have just mentally erased a third of your gold. Always confirm the unit on the scale before any price is discussed.
How they convert
Keep these three relationships in your head and you can sanity-check any quote:
- 1 troy ounce = 31.1035 grams = 20 pennyweights
- 1 gram = 0.643 pennyweights = 0.03215 troy ounces
- 1 pennyweight = 1.5552 grams = 0.05 troy ounces
A fast mental approximation: a pennyweight is about one and a half grams, and a troy ounce is about 31 grams. If a buyer quotes per DWT, roughly two-thirds their number is the per-gram equivalent. That approximation is close enough to catch a lowball on the spot.
A worked example
Say you have a 14K gold chain weighing 20 grams, and the spot price is $4,686 per troy ounce.
- Pure gold price per gram: $4,686 ÷ 31.1035 = $150.66
- 14K is 58.33% pure, so per-gram value of your chain: $150.66 × 0.5833 = $87.90
- Melt value of 20 grams: 20 × $87.90 = $1,758
Now suppose a buyer quotes "$68 per pennyweight for 14K." Your 20 grams is 20 ÷ 1.5552 = 12.86 pennyweights. That is 12.86 × $68 = $874 — under 50% of melt. The per-DWT framing disguised a rip-off. Convert everything to the same unit before you decide.
What about tola, tael, and the rest?
Outside the English-speaking world you will meet still more units: the tola (11.6638 g, standard across the Indian subcontinent), the tael (37.429 g in Hong Kong), the baht (15.244 g in Thailand), and the mesghal (4.6083 g in Iran). Each is legitimate and each has its own regional home. The principle never changes: convert to grams first, find the per-gram value, then multiply. Our weight unit converter handles all of them at once.
The one habit that protects you
Before any transaction, ask one question: "What unit is that scale reading in?" Then convert the quoted price to price-per-gram in your head and compare it to the melt value you calculated at home. Units are not complicated once you pin them down — but leaving them ambiguous is precisely how a careless or dishonest buyer keeps you from noticing a bad offer.