One troy ounce equals exactly 31.1034768 grams (480 grains), the unit platinum (Pt, atomic number 78, CAS 7440-06-4) and every other platinum group metal except osmium is weighed and quoted in. The converter below switches between troy ounces, grams, kilograms, avoirdupois ounces, pennyweight and tola using that single exact factor, feeding DailyPlatinum's wider set of platinum calculators and converters. What follows sets the troy ounce against the everyday avoirdupois ounce, explains why platinum group metals price by the troy ounce at all, and converts it into the regional and historical units still used across bullion trade.
Converter
Exact factors, fixed by definition. No price data.| Unit | Equivalent |
|---|---|
| Grams (g) | 31.1034768 |
| Kilograms (kg) | 0.0311034768 |
| Pennyweights (dwt) | 20 |
| Tola | 2.66666667 |
| Troy pounds (lb t) | 0.0833333333 |
| Grains (gr) | 480 |
| Avoirdupois ounces (oz) | 1.09714286 |
| Avoirdupois pounds (lb) | 0.0685714286 |
What Is a Troy Ounce?#
A troy ounce is a unit of mass equal to 31.1034768 grams, used to weigh precious metals rather than the 28.349523125-gram avoirdupois ounce used for everyday goods. The London Bullion Market Association's glossary defines one troy ounce as exactly 31.1034768 grams, a figure built from a single statutory constant: the grain, fixed at 64.79891 milligrams. Platinum, palladium, rhodium, iridium and ruthenium all price in troy ounces; only osmium, among the platinum group metals, is the exception, priced per gram instead.
Troy Ounce to Grams, Kilograms and Avoirdupois Ounces#
One troy ounce converts to 31.1034768 grams, 0.0311034768 kilograms and 1.0971428571 avoirdupois ounces, using the exact factors in the table below. Every other weight on this page, from the pennyweight to the troy pound, derives from the same 480-grain definition, so a single conversion table covers the full troy system.
| Unit | 1 troy ounce equals |
|---|---|
| Grams | 31.1034768 |
| Kilograms | 0.0311034768 |
| Avoirdupois ounces | 1.0971428571 |
| Pennyweight (dwt) | 20 |
| Tola | 2.6666667 |
| Troy pound | 0.0833333 |
A calculation should always use 31.1034768 grams, never the rounded 31.1, because the gap reaches 3.48 kilograms over 1 million troy ounces, large enough to matter at bullion scale even though it looks trivial per ounce.
What a Troy Ounce Is: History and Troy vs Avoirdupois Ounce#
A troy ounce is defined by one statutory constant, the grain, fixed at exactly 64.79891 milligrams by the International Yard and Pound Agreement of 1 July 1959. Everything else in the troy system, from the pennyweight to the troy pound, is a fixed integer multiple of that one grain value, which is why every conversion in this article resolves to an exact number rather than an approximation.
The Troy Weight Ladder: Grain, Pennyweight, Troy Ounce and Troy Pound#
The troy system builds four units from the same grain: 1 grain, 24 grains to a pennyweight, 480 grains to a troy ounce and 5,760 grains to a troy pound. Each step multiplies the grain count by a fixed factor, so a pennyweight is exactly 1/20 of a troy ounce and a troy pound is exactly 12 troy ounces, the same troy pound used throughout DailyPlatinum's troy weight system reference pages.
| Unit | Grains | Grams | Troy ounces |
|---|---|---|---|
| Grain | 1 | 0.06479891 | 0.00208333 |
| Pennyweight (dwt) | 24 | 1.55517384 | 0.05 |
| Troy ounce | 480 | 31.1034768 | 1 |
| Troy pound | 5,760 | 373.2417216 | 12 |
Jewelers and refiners who need pennyweight-scale conversions for smaller items use the dedicated pennyweight converter, built on the same 1.55517384-gram value shown above.
The 1959 International Yard and Pound Agreement#
Every troy figure in the precious metals trade derives from the 1959 grain definition; a calculation should use 31.1034768 grams, never the rounded 31.1, because the gap reaches 3.48 kilograms over 1 million ounces. The same International Yard and Pound Agreement of 1 July 1959 fixed the avoirdupois pound at exactly 453.59237 grams (7,000 grains), and the troy ounce's 31.1034768-gram value follows from that same grain constant. Every troy and avoirdupois figure on this page, from the pennyweight to the 400-ounce gold bar below, traces back to that one 1959 definition.
Troy Ounce vs Avoirdupois Ounce: The Exact Difference#
A troy ounce is heavier than an avoirdupois ounce by exactly 1.0971428571, because a troy ounce holds 480 grains against the avoirdupois ounce's 437.5 grains. The avoirdupois ounce, at 28.349523125 grams, is the unit on a kitchen scale or a grocery label; the troy ounce, at 31.1034768 grams, is the unit on a bullion invoice. The two units share a name but not a weight, and mixing them in a bullion calculation misstates the result by nearly 10%.
Why Platinum and Other PGMs Are Priced per Troy Ounce#
Platinum, palladium, rhodium, iridium and ruthenium are all quoted in US dollars per troy ounce; osmium is the only platinum group metal priced per gram. The troy ounce became the bullion trade's default unit through the same LBMA and NYMEX market infrastructure that sets the platinum price per troy ounce today, and every dealer quote, exchange contract and refiner base price on this site's price pages carries that same unit.
Which PGMs Are Quoted per Troy Ounce, and Which Is Not#
Platinum (Pt, 78, CAS 7440-06-4) heads a list of five platinum group metals quoted per troy ounce on dealer and exchange screens, with osmium the one exception. The table below names each metal's quote unit and the venue behind it, linking through to that metal's own live price page.
| Metal | Quote unit | Venue | Live price page |
|---|---|---|---|
| Platinum (Pt) | US$ per troy ounce | LBMA Platinum Price; NYMEX futures | platinum price per troy ounce |
| Palladium (Pd) | US$ per troy ounce | LBMA Palladium Price; NYMEX futures | palladium price per troy ounce |
| Rhodium (Rh) | US$ per troy ounce | Johnson Matthey base price; dealer quotes | rhodium price per troy ounce |
| Iridium (Ir) | US$ per troy ounce | Johnson Matthey base price; refiner quotes | iridium price per troy ounce |
| Ruthenium (Ru) | US$ per troy ounce | Johnson Matthey base price; refiner quotes | ruthenium price per troy ounce |
| Osmium (Os) | US$ or EUR per gram | Osmium-Institut daily price | osmium price per gram |
The NYMEX Platinum and Palladium Futures Contract Sizes#
NYMEX prices platinum futures in contracts of 50 troy ounces and palladium futures in contracts of 100 troy ounces, both on CME Group's exchange. Both contracts settle on cast plate or ingot of at least 99.95% fineness, and the 50-ounce and 100-ounce sizes are why market commentary quotes platinum and palladium in round-ounce lots rather than grams or kilograms.
Troy Ounce Conversions for Regional and Historical Units#
Several regional mass units still used in bullion trade convert to an exact fraction of a troy ounce: the tola used across South Asia and the Gulf equals 0.375 troy ounces. Traders moving between London-quoted troy ounces and locally quoted tola or pound figures need an exact factor rather than a rounded one, since local bullion markets settle on their own unit even when the underlying metal is priced internationally in troy ounces.
Troy Ounce to Tola and Pennyweight#
One tola (11.6638038 g) is 3/8 of a troy ounce exactly, fixed by Regulation VII of 1833; ten tolas make the standard ten-tola bullion bar. The tola stays the working bullion unit across India, Pakistan, Bangladesh, Nepal and Gulf markets, converting to a clean fraction of a troy ounce in every case, unlike the pennyweight, whose 1/20-troy-ounce value covers smaller jewelry-scale weights instead of a regional currency of trade.
| Unit | Grams | Troy ounces |
|---|---|---|
| Tola | 11.6638038 | 0.375 |
| Ten-tola bar | 116.638038 | 3.75 |
Full tola-to-gram and tola-to-troy-ounce conversions, including the ten-tola bar, sit on the dedicated tola converter.
Troy Ounce and the Avoirdupois Pound#
A troy pound holds only 12 troy ounces, while an everyday avoirdupois pound holds 14.5833333 troy ounces (453.59237 grams), which is why a "pound" of bullion looks lighter than a pound of ordinary goods. The two pounds share a name for historical reasons only: the avoirdupois pound is the modern commercial pound (453.59237 grams exactly, fixed by the same 1959 agreement), while the troy pound (373.2417216 grams) survives specifically in precious-metals reckoning. Full troy pound conversions are on the troy pound converter.
Other Weight Converters and Platinum Tools#
DailyPlatinum's other weight converters and value tools cover the units and calculations troy-ounce conversions feed into. Each one applies the same exact-factor approach used throughout this page, rather than a rounded shortcut.
Sibling Converters and Value Calculators#
Related converters include the tola, kilogram and gram converters, and the platinum value calculator. Each one shares this page's exact conversion factors rather than a rounded approximation.
- Tola to grams and troy ounces, for South Asian and Gulf bullion units.
- The kilogram to troy ounce converter, for LPPM Good Delivery plates quoted in kilograms.
- The grams to troy ounces converter, for gram-quoted jewelry and dealer invoices.
Troy Ounce FAQ#
Is 1 Ounce the Same as 1 Troy Ounce?#
No, one troy ounce (31.1034768 g) is 9.71% heavier than one avoirdupois ounce (28.349523125 g); they are never interchangeable. A recipe or a package label uses the avoirdupois ounce; a bullion invoice, a coin specification or a PGM price page uses the troy ounce, and confusing the two misstates a metal's value by nearly a tenth.
How Many Grams Are in a Troy Ounce?#
One troy ounce contains 480 grains and equals 31.1034768 grams, exact by definition since 1 July 1959. That figure never rounds in a bullion calculation, since the difference from the shorthand 31.1 grams grows to 3.48 kilograms over a million ounces.
Why Is a Pound of Gold Only 12 Troy Ounces?#
A pound of gold reads as only 12 ounces when it is priced as a troy pound (12 troy ounces), not an everyday avoirdupois pound (16 avoirdupois ounces, 14.5833 troy ounces). Bullion has used the troy pound since before the 1959 agreement standardized the modern avoirdupois pound for commercial goods, so the two "pounds" never described the same weight of metal.
How Much Does a 400-Ounce Gold Bar Weigh?#
A "400-ounce" London Good Delivery gold bar actually weighs between 350 and 430 fine troy ounces (about 10.9 to 13.4 kilograms), not exactly 400 troy ounces; 400 oz is the trade nickname, not the specification. The LBMA's Good Delivery technical specifications set that weight range along with a minimum fineness of 995.0 parts per thousand, so individual bars within the range never carry an identical weight.
What Is a Troy Pound?#
A troy pound equals 12 troy ounces (373.2417216 grams), a separate unit from the 453.59237-gram avoirdupois pound. It is built from the same 5,760-grain chain as the rest of the troy system; full conversions are on the troy pound converter.
What Are Platinum's Symbol, Atomic Number and CAS Number?#
Platinum has the symbol Pt, atomic number 78 and CAS number 7440-06-4, and like the other platinum group metals it is conventionally weighed and quoted in troy ounces. PubChem's element record lists platinum's atomic mass at 195.08, alongside the same identity data that anchors every platinum page on this site.