The Numbers
1 troy ounce = 31.1035 grams
1 avoirdupois ("regular") ounce = 28.3495 grams
1 troy ounce = 1.09714 avoirdupois ounces (about 9.7% heavier)
1 avoirdupois ("regular") ounce = 28.3495 grams
1 troy ounce = 1.09714 avoirdupois ounces (about 9.7% heavier)
Grocery scales, body-weight scales and shipping labels use the avoirdupois ounce. Gold, silver, platinum and palladium prices — anywhere you see "$/oz" for a precious metal — use the troy ounce instead, a convention from medieval European bullion trading that's stuck around as the modern international standard.
Why It Matters
Mixing the two up when comparing a precious-metals price against an everyday weight (or a bullion bar's spec sheet) can lead to a meaningfully wrong value — a troy ounce is about 9.7% heavier, which is not a rounding error at any real quantity of gold. If a source doesn't specify which ounce it means for a metals weight, troy is the safe default assumption.
Other Pages
Gold Price Per Ounce
Troy ounce, bullion standard
Scrap Gold Calculator
Mixed lot, multiple items
Is My Gold Real?
Hallmark, magnet & water tests
Methodology
Data source & formula
Main Calculator
All karats in one tool
Frequently Asked Questions
A troy ounce is 31.1035 grams — heavier than the 28.3495-gram avoirdupois ("regular") ounce used for everyday items like food or body weight.
The troy ounce is a centuries-old unit from medieval European bullion trading that became the international standard for precious metals — gold, silver, platinum and palladium are all quoted in troy ounces by convention, not regular avoirdupois ounces.
Yes — in the precious metals and bullion industry, "oz" or "ounce" without further qualification means troy ounce by default. This is different from most other contexts (food, shipping, body weight), where "ounce" means the avoirdupois ounce instead.
No — a troy pound is 12 troy ounces (not 16, like an avoirdupois pound), which is why gold weight is almost always discussed in ounces or grams rather than pounds, to avoid that extra layer of confusion.