How many grams to a Troy ounce
Executive summary
One troy ounce equals 31.1034768 grams (commonly rounded to 31.1035 g), the unit used worldwide for precious metals and gemstones [1] [2]. The troy ounce differs from the common avoirdupois ounce (28.349523125 g), so using the wrong ounce can produce nearly a 10% error in weight-based pricing [3] [4].
1. What a “troy ounce” actually is — quick definition
The troy ounce is a mass unit from the troy weight system, historically used for coins, gemstones and precious metals; by definition it equals 480 grains and therefore 31.1034768 grams [5] [6]. Modern online converters and reference pages consistently list 1 oz t = 31.1034768 g [1] [3].
2. Why that number matters in markets
Gold, silver and platinum are quoted and settled in troy ounces, so a quoted price per “ounce” in bullion markets implies the 31.1034768 g troy ounce; confusing it with the common (avoirdupois) ounce at 28.349523125 g would under- or over-value metal by roughly 9.7% [3] [4]. Multiple converter sites and precious-metals resources emphasize that the troy ounce is the industry standard for bullion [3] [7].
3. Historical and technical origin — where the 31.1034768 g comes from
The troy ounce is composed of 480 grains; a grain is fixed at 0.06479891 grams, so 480 × 0.06479891 g = 31.10347680 g — the precise figure used in technical references and Wikipedia’s description of troy weight [5]. This grain-based derivation explains the exactness reported by unit converters [6] [1].
4. How sites and converters report the figure — small differences in rounding
Commercial converters and calculators commonly show 1 troy ounce ≈ 31.1035 g for readability, while more exact tools give 31.1034768 g or 31.10347680 g; both forms come from the same underlying definition but differ only by formatting and rounding choices [2] [1] [6].
5. The troy ounce vs. the avoirdupois ounce — practical implications
The avoirdupois ounce (used in everyday U.S./UK measurements) equals 28.349523125 g, about 2.754 g lighter than the troy ounce; this is why jewelers, mints and bullion dealers always specify “troy” when quoting ounces [3] [4]. Conversion mistakes between the two ounce types produce material pricing and inventory errors, so explicit labeling matters in contracts and price feeds [3].
6. Where the troy ounce is still used and where it’s been replaced
Most precious-metals markets, international bullion pricing, and many national central-bank gold statistics use troy ounces [3] [5]. Some issuers and jurisdictions (noted as an example in reporting) have shifted or additionally specify grams for coins and bullion — for instance, China’s bullion coins are described in grams in some official practice, though details about widespread legal replacement are not fully covered in the cited pages [5]. Available sources do not mention a comprehensive global phase-out of the troy ounce.
7. How to convert — simple formulas and checks
To convert troy ounces to grams multiply by 31.1034768; to go the other way divide grams by 31.1034768. Many online calculators implement these exact factors and display rounded outcomes for convenience [1] [8]. If precision matters (tax reporting, bullion settlement), use the full 31.1034768 figure cited in technical resources [6] [5].
8. Caveats, rounding and best practice
Public-facing pages often round to 31.1035 g; that rounding is harmless for casual use but can matter in high-value transactions. Always confirm whether a quoted “ounce” on pricing screens means “troy ounce” (oz t/ozt) or avoirdupois ounce and request gram equivalents in contracts to avoid ambiguity [2] [3].
Limitations: this summary uses only the provided sources. For legal or contractual decisions about bullion weight, consult primary standards or official mint/market documentation; those specifics are not exhaustively covered in the cited converter and encyclopedia excerpts [1] [5].