Quick answer
One troy ounce is exactly 31.1034768 grams, exactly 20 pennyweights (dwt), or 480 grains. Every legitimate scrap, jewelry, or bullion transaction should reconcile to those numbers. When they do not, the disagreement is almost always because a buyer quoted a rate in one unit and paid in another, or because the everyday grocery-store ounce (28.35 grams) was quietly substituted for the troy ounce.
The three units gold moves in, and one that does not belong
Gold, silver, platinum, and palladium in the United States are weighed under the troy system, not the everyday (avoirdupois) system used for groceries. That single distinction is the source of most disputes at the counter. The NIST Handbook 44, which governs commercial weighing in every state, requires scales used in precious metals commerce to display troy units when transactions are conducted in troy weight.
Four units matter for any seller:
- Grain. The smallest historical unit, still used for firearms. Twenty-four grains equal one pennyweight. Rarely quoted for jewelry today.
- Pennyweight (dwt). Twenty-four grains, or one-twentieth of a troy ounce. The unit most American jewelers and dental gold buyers use on their price sheets.
- Gram. The metric unit used on almost every digital jewelry scale worldwide.
- Troy ounce (ozt). The unit spot prices are quoted in. When you see a headline “gold hits $3,300 per ounce,” that ounce is a troy ounce. It is the settlement unit for the London Bullion Market Association.
The unit that does not belong in a precious metals transaction is the avoirdupois ounce, the one printed on cereal boxes and postal scales. One avoirdupois ounce is 28.349523125 grams, roughly 9.7 percent lighter than a troy ounce. Confusing the two, deliberately or accidentally, understates a seller’s payout by that same percentage on every ounce.
The full conversion table
Every value below is exact by international definition. Save this table before comparing dealer quotes.
| Unit | Grams | Pennyweights (dwt) | Troy ounces (ozt) | Grains |
|---|---|---|---|---|
| 1 grain | 0.06479891 g | 0.04167 dwt | 0.00208 ozt | 1 |
| 1 gram | 1 | 0.6430 dwt | 0.03215 ozt | 15.4324 grains |
| 1 pennyweight | 1.5551738 g | 1 | 0.05 ozt | 24 |
| 1 troy ounce | 31.1034768 g | 20 | 1 | 480 |
| 1 troy pound | 373.2417216 g | 240 | 12 | 5,760 |
| 1 avoirdupois ounce (not for metals) | 28.3495231 g | 18.2291 dwt | 0.9114583 ozt | 437.5 grains |
The critical row is the last. An avoirdupois ounce is about 9.7 percent lighter than a troy ounce. A dealer who quotes “per ounce” without specifying which is either sloppy or setting up an unnamed discount.
Why American jewelers still quote in pennyweights
The pennyweight is a medieval English unit, originally the weight of one silver penny minted in the 12th century. The abbreviation “dwt” preserves the Latin word for penny (denarius). At roughly 1.55 grams, it is a coarse enough increment that a jeweler weighing a wedding band does not have to record three decimal places, and 20 dwt lines up cleanly with one troy ounce of casting grain. Dental laboratories and refineries adopted the same unit and never abandoned it.
The consequence for sellers: two buyers can quote what sounds like the same rate and still produce very different offers, purely because one pays in dwt and the other in grams.
How buyers use unit confusion to underpay
The Federal Trade Commission and multiple state consumer protection offices treat unit-switching as a documented pattern in scrap gold and cash-for-gold operations. Three variations show up most often. Recognizing them before you weigh anything is the difference between a fair offer and a quiet 10 to 40 percent discount.
Quoting in pennyweights when the seller assumes grams
A buyer says “we pay $60 per pennyweight for 14K.” A seller who does not know the unit assumes it means grams. The actual payout works out to roughly $38.58 per gram. The offer is not necessarily unfair, but the seller who assumed grams walks in expecting nearly 60 percent more than they will receive.
Quoting per ounce without specifying troy
Signage reads “we pay $2,800 per ounce of pure gold.” An avoirdupois scale reads 5.00 ounces for a piece that actually contains 4.56 troy ounces: the seller loses roughly 9.7 percent before any refining discount. Reputable dealers always clarify per troy ounce. If the quote does not, ask.
Weighing in one unit, paying in another
The most damaging pattern is a buyer who weighs in grams (displayed on the scale) but calculates payment as if the weight were in pennyweights. Treating a gram reading as pennyweights understates the payout by a factor of 1.55. NIST Handbook 44 requires the unit label to be visible on the scale: always ask to see it.
Three worked examples using current spot prices
The examples below use a placeholder spot price of $3,300 per troy ounce for arithmetic clarity. Substitute the current spot at the moment of your transaction. Live spot prices are published by the London Bullion Market Association and republished on every major dealer site. All values assume pure (24K) gold; multiply by the purity fraction for karat gold (0.583 for 14K, 0.750 for 18K, 0.9167 for 22K).
Example 1: converting a dwt quote to a gram equivalent
A refinery quotes $95 per pennyweight for 24K gold. Divide by 1.5551738 to get $61.09 per gram, or $1,900 per troy ounce (95 × 20). Against spot near $3,300, that is roughly 57.6 percent of spot: a reasonable scrap-refinery payout, though not competitive with the 80 to 90 percent bullion dealers pay for recognized bars and coins.
Example 2: converting a 14K jewelry lot from grams to a dollar figure
A jeweler weighs your 14K chain lot at 47.5 grams. Convert to troy ounces: 47.5 ÷ 31.1034768 = 1.5272 ozt of alloy. Multiply by the 14K purity fraction (0.583): 0.8903 ozt of pure gold. At spot $3,300, the metal content is worth $2,938. Scrap buyers typically pay 70 to 85 percent, putting a fair offer in the $2,056 to $2,497 range.
Example 3: reading a bullion coin’s stated weight
The American Gold Eagle contains exactly one troy ounce of pure gold (31.1034768 g), but its total weight is 33.931 g because the U.S. Mint alloys it with copper and silver for durability. On a gram scale, the reading is 33.931 g, not 31.1. The extra 2.8 g is alloy, and the pure gold content is guaranteed by U.S. Mint specifications. Any buyer who deducts pay for the “extra” weight is misreading the spec.
Compare offers before you accept any single quote
Once you have converted every offer to a common unit (dollars per gram of pure gold), the fair one is the highest that clears your walk-away floor. Rather than driving to three dealers with your pieces, submit one free request on Goldiew’s sell gold page and receive sealed bids from up to 15 verified precious metals buyers. Every bid arrives in writing with the unit, spot price, and purity assumptions the buyer used, so unit-switching is impossible. You can also browse active listings on the Goldiew marketplace to see what comparable pieces are trading for before deciding.
Frequently asked questions
How much is one pennyweight of gold worth today?
The dollar value depends on current spot and the karat of the gold. For pure (24K) gold at a spot of $3,300 per troy ounce, one pennyweight of gold contains 1.5551738 grams of pure metal and is worth $165.00 at spot ($3,300 ÷ 20). For 14K gold, multiply by the purity fraction 0.583, giving $96.21 per pennyweight at spot. Scrap buyers typically pay 70 to 85 percent of that figure to cover refining and margin. Recalculate at the current spot published by the LBMA before comparing offers.
Is a troy ounce heavier or lighter than a regular ounce?
A troy ounce is heavier. One troy ounce equals 31.1034768 grams; one avoirdupois (regular) ounce equals 28.349523125 grams. The troy ounce is about 9.7 percent heavier. A dealer who says “per ounce” without specifying troy is either quoting the smaller avoirdupois ounce, which understates a seller’s fair payout by roughly 9.7 percent on the metal, or leaving the unit ambiguous. Reputable precious metals transactions always specify troy.
How do I convert grams to pennyweights on a jewelry scale?
Divide the gram reading by 1.5551738 to get pennyweights. For example, 10 grams is 10 ÷ 1.5551738 = 6.4301 dwt. Many digital jewelry scales include a dwt mode that displays both units on demand; check the manual for the unit-switch button. If you are comparing a buyer’s dwt quote to your own gram measurement, always convert first before evaluating the offer.
Why do American jewelers use pennyweights when the rest of the world uses grams?
Pennyweights are a legacy of the medieval English weight system that never left the U.S. jewelry trade. A pennyweight (about 1.55 g) is a convenient increment for hand-weighing small pieces, and 20 dwt equals exactly one troy ounce. Dental gold buyers, casting suppliers, and estate jewelers standardized on the unit and kept it. Bullion dealers and the international market use troy ounces or grams instead.
How many grams are in a troy ounce of gold?
Exactly 31.1034768 grams. This is a defined constant, not a rounded figure. The definition comes from the international agreement on customary units and is documented in NIST Handbook 44, which governs commercial scales in every U.S. state. Every legitimate spot price, dealer quote, and bullion product specification uses this number as the reference.
What is the karat purity of gold in terms of the conversions?
Karat measures purity, not weight. 24K = 0.9999, 22K = 0.9167, 18K = 0.750, 14K = 0.583, 10K = 0.417. To find pure gold content, multiply total weight by the karat fraction. A 20-gram 14K chain contains 20 × 0.583 = 11.66 grams of pure gold (0.3749 troy ounces).
Do bullion coins really weigh exactly one troy ounce?
Bullion coins contain exactly one troy ounce of pure metal, but total coin weight is often higher due to alloy added for durability. The American Gold Eagle weighs 33.931 g total but contains 31.1034768 g of pure gold. The 99.99 percent pure American Gold Buffalo weighs almost exactly 31.1 g. Every mint (U.S. Mint, Royal Canadian Mint, Perth Mint) lists total and pure weight separately.
Sources
- NIST Handbook 44: Specifications, Tolerances, and Other Technical Requirements for Weighing and Measuring Devices (troy vs. avoirdupois definitions; scale marking requirements)
- NIST Office of Weights and Measures publications (customary weight system definitions used throughout this guide)
- London Bullion Market Association: Precious Metal Prices (spot price reference market and troy ounce settlement unit)
- United States Mint: American Eagle Coin Program (bullion coin specifications and pure metal content)
- Federal Trade Commission: Jewelry Shopping Tips (weight and purity disclosure standards for precious metals)