Ounces vs Troy Ounces: Understanding the Bullion Trading Standard

At The Coin Chest™, we often get asked why precious metals are traded in troy ounces instead of the ounces most people are familiar with. The answer lies in history, standardisation, and accuracy in trade.

The Difference Between Ounces and Troy Ounces

Most bullion dealers, including ourselves, will list coins using the shorthand “oz”. This always refers to troy ounces in the bullion world, not the everyday ounce used for food or goods.

  • Avoirdupois Ounce (Standard Ounce): Used for everyday items like food and household goods. Equal to 28.35 grams.
  • Troy Ounce: The global standard for bullion. Equal to ≈ 31.1035 grams.
  • 1 Troy Ounce = 1.097 Ounces

The extra ~10% weight makes a big difference when buying or selling gold and silver.

Quick Conversion Guide

  • 1 troy ounce = 31.1035 grams
  • 1 standard ounce = 28.35 grams
  • 1 kilogram = 32.15 troy ounces

For investors, knowing these numbers is crucial to avoid confusion between weights and pricing.

The Origins of the Troy Ounce

The troy system dates back to the Middle Ages in Troyes, France, a major trading hub. Merchants from across Europe needed a consistent standard to settle trade in silver and gold. Defined as 480 grains of barley, the troy ounce gave merchants a consistent unit of measure. Over time, the system became recognised across Europe and was later adopted by the British Royal Mint in the 1500s, before becoming the “gold standard” (pun intended) by 1527 as stated by London Bullion Market Association (LBMA).

By 1828, the troy ounce was firmly established as the international unit for precious metals, when the United States of America also standardised on this unit of measure. Today, it remains the trusted standard for gold, silver, platinum, and palladium.

Why the Troy Ounce Became the Standard

  • Consistency in Trade – Ensured that merchants across nations were weighing the same quantity.
  • Historical Precedent – Centuries of usage embedded the troy system in bullion markets.
  • Global Trust – Precious metals dealers, refiners, and investors rely on one universal unit to avoid disputes.

Why This Matters for Buyers and Sellers

When buying or selling bullion, always double check whether the weight is listed in troy ounces. Most modern coins, bars, and rounds are minted to this standard worldwide. However, there are some exceptions where bullion coins aren’t minted to the troy ounce standard, like the Chinese silver 30.00g bullion rounds issued by People’s Bank of China. Hence, using the wrong unit can create major misunderstandings in valuation.

At The Coin Chest™, all our bullion products are quoted transparently, ensuring our customers know exactly what they are getting.

Trust in Tradition

The troy ounce is a link to centuries of trade, a safeguard for accuracy, and a foundation of trust in the bullion market. By understanding the difference, you protect yourself from costly mistakes and gain confidence in every transaction. If you found this guide helpful, be sure to check out how much is 1kg of silver worth.