1 oz of Gold = How Many Grams?
When you hear “1 oz of gold,” it’s easy to assume it’s the same ounce you use when weighing flour or postage stamps. In fact, precious metals like gold use the troy ounce, which is heavier: 1 troy ounce of gold equals 31.1035 grams. By contrast, the standard (avoirdupois) ounce—used in most everyday measurements—weighs 28.3495 grams. This article explains where those numbers come from, why the troy ounce matters for investors, and how to convert between units with ease.
Table of Contents
- What Is an Avoirdupois Ounce?
- What Is a Troy Ounce?
- Comparison: Troy vs. Avoirdupois
- Conversion Formulas
- Why the Difference Matters for Gold
- How to Convert Quickly
- FAQs
What Is an Avoirdupois Ounce?
The avoirdupois ounce is the “ounce” most people know. It’s part of the avoirdupois system, historically used in the U.S. and U.K. for everyday goods (produce, postal parcels, etc.). By definition:
- 1 avoirdupois ounce (oz) = 28.3495 grams
- 16 avoirdupois ounces = 1 avoirdupois pound (453.592 grams)
This system simplifies retail and shipping calculations but isn’t used for precious metals.
What Is a Troy Ounce?
The troy ounce dates back to medieval trade fairs in Troyes, France, becoming the standard for precious metals—gold, silver, platinum—because of its fine-grained accuracy. Its key defining points:
- 1 troy ounce (oz t) = 31.1035 grams
- 12 troy ounces = 1 troy pound (373.2417 grams)
Although the troy pound has largely fallen into disuse, the troy ounce remains firmly entrenched in bullion markets worldwide.
Comparison: Troy vs. Avoirdupois
| Unit | Abbreviation | Grams |
|---|---|---|
| Avoirdupois Ounce | oz | 28.3495 g |
| Troy Ounce (Precious Metals) | oz t | 31.1035 g |
The troy ounce is approximately 9.7% heavier than the standard ounce. When you buy or sell gold, the market quote always refers to troy ounces.
Conversion Formulas
// To convert between ounces and grams:
Troy ounce → grams:
grams = ounces × 31.1035
Avoirdupois ounce → grams:
grams = ounces × 28.3495
Grams → troy ounces:
troy ounces = grams ÷ 31.1035
Example: How many grams are in 2.5 troy ounces of gold?
2.5 oz t × 31.1035 g/oz t = 77.75875 g
Why the Difference Matters for Gold
- Pricing Precision: Gold is traded in troy ounces on global exchanges (e.g., COMEX, LBMA). A small miscalculation can translate into significant monetary value when dealing with large quantities.
- Purity Calculations: Hallmarking and purity (e.g., 24 K vs. 18 K) use troy ounces as the baseline, so conversion accuracy ensures you’re getting exactly the weight and fineness you pay for.
- Historical Consistency: Long-term gold price charts and investment records are expressed in troy ounces—switching systems midstream would disrupt continuity.
How to Convert Quickly
- Mental Shortcut: To approximate, multiply troy ounces by
31.1instead of 31.1035; multiply standard ounces by28.35. - Smartphone Widget: Many bullion apps include built-in ounce-to-grams converters. A simple JavaScript snippet on your own site can let visitors input ounces and instantly see grams.
- Spreadsheet Formula: In Excel or Google Sheets, use
=A2*31.1035(where A2 contains the ounce value).
FAQs
Why does gold use the troy ounce instead of the standard ounce?
Gold’s historical trade routes adopted the troy system for its fine granularity and consistency across regions. Even today, it remains the universal standard for bullion markets.
Is the troy ounce used for any other metals?
Yes—silver, platinum, and palladium are also quoted in troy ounces. Industrial metals (copper, aluminum) use metric tonnes or pounds.
Can I mix troy and avoirdupois ounces in recipes or jewelry making?
No—always stick to one system. If you use troy ounces in jewelry, ensure your tools and alloy measurements match the troy standard to maintain purity and weight accuracy.