GOLD USD 4,142.01 / oz • Δ USD +43.82 +1.07% GOLD USD 133,168.71 / kg • Δ USD +1,408.85 +1.07% 1W -1.98% 1M +9.33% 1Y +50.56%

Troy Ounce

A troy ounce is the standard unit of measurement used to value and trade gold, silver, platinum, and other precious metals in global markets.
Equal to 31.1034768 grams, the troy ounce remains the cornerstone of bullion pricing, settlement, and inventory reporting across all major financial and refining systems.

Unlike the more common avoirdupois ounce used for everyday goods (28.3495 grams), the troy ounce is reserved exclusively for precious metals and gemstones, preserving historical precision in trade and valuation.

Definition and Conversion

One troy ounce (oz t) equals 31.1034768 grams or 1/12 of a troy pound, which is equivalent to 373.2417216 grams.
This measurement standard ensures that all gold, silver, and platinum bars are valued and traded on a consistent, globally recognized basis.

Conversion references:

  • 1 troy ounce = 31.1034768 grams
  • 1 kilogram = 32.1507466 troy ounces
  • 1 metric ton = 32,150.7466 troy ounces

Thus, a 400 oz Good Delivery bar weighs approximately 12.4 kilograms.

Historical Background

The troy ounce originated in Troyes, France, a medieval trading city known for its fairs where merchants from across Europe standardized weights for precious metals and luxury goods.
By the 14th century, the troy system was adopted by the English Royal Mint and later became the global standard for precious metals.

In 1824, the British Imperial system formally adopted the troy ounce for bullion, and in 1828 the United States Mint incorporated it into coinage and refining operations.
Since then, it has remained the universal metric of gold trade, from refineries to exchanges such as COMEX, LBMA, and the Shanghai Gold Exchange.

Usage in Precious Metals Markets

All professional bullion transactions, including futures contracts, custody reports, and central bank reserves, use the troy ounce as the base unit of measure.
Examples include:

  • Spot and futures quotes: USD per troy ounce;
  • Refinery output: measured and stamped in troy ounces;
  • Vault barlists: recorded by weight in troy ounces;
  • Institutional reports: reconciled in troy ounces for comparability.

This universal standard enables seamless conversion and valuation across markets, vaults, and jurisdictions.

Application in Refining and Custody

Refineries, vaults, and custodians rely on the troy ounce for precise weight recording and audit verification.
Barlists and audit reports list each bar’s troy ounce weight, fineness, and total troy ounces per client account.

For example:

  • A 400 oz bar = 400 troy ounces × fineness (e.g., 0.9999) = 399.96 fine troy ounces of gold content.
  • A 100 oz bar = 100 troy ounces × 0.9999 = 99.99 fine troy ounces.

These calculations ensure that valuation and ownership reporting remain consistent across the global custody network.

Regulatory and Market Standards

Institutions using the troy ounce system include:

  • London Bullion Market Association (LBMA) — sets Good Delivery weight and purity standards;
  • COMEX (CME Group) — defines gold futures contracts at 100 troy ounces per unit;
  • World Gold Council (WGC) — reports market data and demand using troy ounces;
  • Refineries and mints worldwide, maintaining weight conformity for assay and certification.

All professional vault audits and insurance valuations reference troy ounce weights, making it the definitive legal and financial unit of bullion measure.

Institutional and Analytical Role

The troy ounce provides a uniform valuation baseline for global gold trading and custody.
It allows precise comparison of reserves, investment products, and storage reports across institutions and jurisdictions.
By preserving historical continuity and mathematical precision, the troy ounce remains the universal language of gold measurement — bridging refining, storage, and settlement into one standardized unit.

Related Posts