There are 31.1035 grams in a troy ounce, the ounce used for gold, silver and platinum, and 28.3495 grams in the ordinary (avoirdupois) ounce used for food and postage, so an ounce of gold is about 9.7% heavier than an ounce of sugar. The exact figure, 31.1034768 g, is the definition in the 2026 edition of the NIST Handbook 44, Appendix C. At the Ask on 3 November 2026 (6:47 pm New York time), a gram of gold is $127.27 and a gram of silver $1.61, against $3,958.46 and $50.18 for a troy ounce.
Weight also decides what you pay per gram. In Bullion Trading LLC price records since 27 October 2024, the median premium over the Ask was 31.6% for a 1 gram bar and 1.7% for a 1 kilo bar, so at today's Ask the gold in a 1 gram bar costs about $167.47 a gram against $129.43 in a kilo bar. Below: the conversions, a converter for every unit gold is sold in, what an ounce looks like, karat gold, and the price per gram over time.
| Key finding | Result |
|---|---|
| Grams in a troy ounce (gold, silver, platinum) | 31.1035 g (exactly 31.1034768 g) |
| Grams in an ordinary (avoirdupois) ounce | 28.3495 g (exactly 28.349523125 g) |
| Difference | A troy ounce is 2.754 g, or 9.7%, heavier |
| Troy ounces in a kilo | 32.1507 |
| Gold Ask, 3 Nov 2026 | $3,958.46 an ounce, $127.27 a gram |
| Silver Ask, 3 Nov 2026 | $50.18 an ounce, $1.61 a gram |
| Median premium, 1 g bar vs 1 kilo bar | 31.6% vs 1.7% over the Ask (since 27 October 2024) |
Why does gold use the troy ounce?
Because precious metals have always been weighed in troy units, and the law kept it that way. The system takes its name from Troyes, a medieval market town in France. Congress adopted the troy pound as the standard for U.S. coinage on 19 May 1828 (NIST), and gold prices worldwide are still quoted in U.S. dollars per troy ounce.
Both ounces are built from the same grain of 64.79891 milligrams. A troy ounce is 480 grains; an ordinary ounce is 437.5 grains. Since the 1959 international agreement that fixed the pound at exactly 0.45359237 kg, both have exact metric values.
Myth: a pound of gold weighs more than a pound of feathers. Fact: a troy pound is only 12 troy ounces, 373.24 g, against 453.59 g for an ordinary pound. The troy ounce is heavier; the troy pound is lighter.
How many grams is half an ounce, or a quarter ounce?
Half a troy ounce is 15.552 g and a quarter troy ounce is 7.776 g. Half an ordinary ounce, the one in recipes, is 14.175 g, and a quarter is 7.087 g. Bullion coins and bars marked 1/2 oz or 1/4 oz always use the troy ounce. Half a troy ounce of gold, 15.55 g, is $1,979.23 at today's Ask.
| Size | Troy ounce (gold) | Ordinary ounce (food) | Gold at the Ask |
|---|---|---|---|
| 1/20 oz | 1.555 g | 1.417 g | $197.92 |
| 1/10 oz | 3.110 g | 2.835 g | $395.85 |
| 1/4 oz | 7.776 g | 7.087 g | $989.62 |
| 1/2 oz | 15.552 g | 14.175 g | $1,979.23 |
| 1 oz | 31.1035 g | 28.3495 g | $3,958.46 |
| 10 oz | 311.03 g | 283.50 g | $39,584.60 |
What does an ounce of gold look like?
Smaller than most people expect. Gold weighs 19.3 grams per cubic centimeter, about 1.7 times as much as lead, so a troy ounce melted into a cube would measure 11.7 mm on a side, under half an inch. A kilo would be a cube 37.3 mm across.
Real coins and bars spread that metal thin. The 1 oz American Gold Eagle and American Buffalo are both 32.70 mm (1.29 inches) across.
How many grams of gold are in a 22K ounce?
A full 31.1035 g in a bullion coin, because the mint adds the alloy on top. The 1 oz American Gold Eagle is 22 karat (91.67% gold, 3% silver, the rest copper) and weighs 33.931 g, which holds exactly one troy ounce of gold, according to the U.S. Mint. At today's Ask that ounce of gold is $3,958.46, the same as the gold in a 31.1 g bar.
Jewelry works the other way: 31.1 g of 14K chain holds 18.20 g of gold. The British Sovereign weighs 7.98 g and contains 7.32 g of gold, 0.2354 troy oz (The Royal Mint).
| Karat | Fineness | Fine gold in 31.1 g of alloy | Gold value per gram of alloy | Typical use |
|---|---|---|---|---|
| 24K | 999.9 | 31.10 g | $127.25 | Bars, Maple Leaf, Buffalo, Philharmonic |
| 22K | 916.7 | 28.51 g | $116.67 | American Gold Eagle, Krugerrand, Sovereign |
| 18K | 750 | 23.33 g | $95.45 | Fine jewelry |
| 14K | 585 | 18.20 g | $74.45 | Everyday jewelry |
| 10K | 417 | 12.96 g | $53.03 | Budget jewelry |
How much does a gram of gold cost today?
$127.27 (Ask) a gram at spot, and silver $1.61 (Ask). Spot is the wholesale price of an ounce of 999.9 gold divided by 31.1035; nobody sells a single gram at spot. A year earlier a gram cost $129.41; at the start of 2000 it cost $9.05.
Why do small gold bars cost more per gram?
Because the cost of making, assaying, packing and handling a bar is roughly the same whatever it weighs, and a 1 g bar spreads it over one gram. In our price records since 27 October 2024 the median premium falls from 31.6% over the Ask for a 1 g bar to 7.9% for 10 g, 2.7% for 1 oz and 1.7% for a kilo.
Today’s prices tell the same story. These are our own prices, one dealer’s snapshot, and each size links to the bar it quotes.
| Size | Same weight in | Bar price today | Per gram of gold | Over the Ask |
|---|---|---|---|---|
| 1 g bar | 0.0322 oz | $166.29 | $166.31 | 30.7% |
| 2.5 g bar | 0.0804 oz | $375.23 | $150.11 | 17.9% |
| 5 g bar | 0.1608 oz | $726.46 | $145.31 | 14.2% |
| 10 g bar | 0.3215 oz | $1,383.93 | $138.41 | 8.8% |
| 20 g bar | 0.6430 oz | $2,699.85 | $135.01 | 6.1% |
| 1 oz bar | 31.10 g | $4,075.14 | $131.03 | 3.0% |
| 50 g bar | 1.608 oz | $6,714.63 | $134.31 | 5.5% |
| 100 g bar | 3.215 oz | $13,069.25* | $130.71 | 2.7% |
| 10 oz bar | 311.0 g | $40,881.42 | $131.45 | 3.3% |
| 1 kilo bar | 32.151 oz | $130,389.77 | $130.41 | 2.5% |
For buyers who want grams for jewelry work rather than to hold, 24K casting grain sold by the ounce is usually the cheapest gram; for holding, see our fractional gold guide.
How weight is shown on our product pages
- Name and Weight field: gram bars are listed in grams (“10 Gram Gold Bar”), coins and ounce bars in troy ounces (“1 oz”).
- Every “oz” on a product page is a troy ounce.
- Metal weight: bar specifications add the weight in troy ounces, so a 1 g bar shows 0.03215 troy oz.
- Purity: shown as a percentage or fineness, for example 99.99% or .9167 (22 karats).
- Price: set from the live spot price times the fine metal weight, plus a premium per product.
Kilos, tolas, taels and baht
| Unit | Grams | Troy ounces | Where it is used |
|---|---|---|---|
| Kilo | 1,000 | 32.1507 | Large bars, worldwide |
| Tael (troy) | 37.429 | 1.2034 | Hong Kong gold market |
| Baht | 15.244 | 0.4901 | Thailand, 96.5% gold bars |
| Tola | 11.6638 | 0.375 | India, Pakistan, the Gulf |
| Pennyweight (dwt) | 1.5552 | 0.05 | U.S. jewelers and scrap buyers |
| Grain | 0.0648 | 1/480 | Ammunition, old coin standards |
Scrap buyers often weigh in pennyweights, 20 to the troy ounce; our pennyweight vs gram guide shows how the unit changes a payout.
How we did the research
Conversions use the exact NIST definitions. Prices per gram divide the Ask, the price level dealers quote for buying, from the store’s live feed, by 31.1034768. Premiums by size are medians of the daily premium of the random-brand bar in each size (its recorded check/wire price over the value of its gold at that day’s spot close, converted to the Ask the same way as today’s numbers) since 27 October 2024, so no single day shapes the curve. Bars with shorter records are starred. The history chart uses LBMA prices to 28 September 2026 and our recorded 5 pm New York closes after that.
Limits: premiums are one dealer’s and move with spot; named-brand bars usually cost more. See the live gold price chart for spot by the minute.
Bottom line
Gold’s ounce is the troy ounce: 31.1035 g, 9.7% more than the kitchen ounce. Check whether a weight is gross or fine before comparing prices, and compare small bars by price per gram of gold, not per bar.
FAQ
Is an ounce of gold 28 grams or 31 grams?
31.1035 g. The 28.35 g ounce is the ordinary ounce; gold, silver and platinum are always weighed in troy ounces.
How many grams is 1 ounce of 22K gold?
A 1 oz 22K bullion coin weighs about 33.93 g and contains 31.1035 g of gold. 31.1 g of 22K jewelry contains 28.51 g of gold.
Is an “ons” the same as an ounce?
No. In Indonesian and Dutch an ons is 100 grams. Gold prices quoted per ounce mean the troy ounce of 31.1035 g.
How many troy ounces are in a kilo?
32.1507, so a kilo bar holds a little over 32 ounces of gold. Our gold fineness guide explains the purity marks on bars and jewelry.
Sources
- NIST, Handbook 44 (2026), Appendix C: troy, avoirdupois, pennyweight and grain definitions.
- NIST, A Brief History of the Office of Weights and Measures: the 1828 troy pound for coinage.
- BIPM, The International System of Units (SI): the kilogram and gram.
- U.S. Mint, bullion coin programs and coin specifications: Gold Eagle, Buffalo and quarter.
- The Royal Mint, Sovereign: weight and gold content.
- Los Alamos National Laboratory, Periodic Table: Gold: density.
- Hong Kong e-Legislation, Weights and Measures Ordinance, Cap. 68: the troy tael.
- Singapore Bullion Market Association, Thailand’s gold market: the 15.244 g baht.
- LBMA, precious metal prices: gold price history to 28 September 2026, shown as charts only.