Troy Ounce vs Regular Ounce — Gold Weight Explained
A troy ounce equals 31.1035 grams. It is the universal unit for quoting gold prices — not the common (avoirdupois) ounce of 28.3495 grams used for food or postal weights. Using the wrong ounce will undervalue gold by 9.7%. Always use troy ounces for any gold calculation.
Weight Conversion Reference Table
From
Equals
Notes
1 Troy Ounce (oz t)
31.1035 g
Gold pricing standard
1 Troy Ounce (oz t)
0.0311 kg
1 Troy Ounce (oz t)
2.6667 tola
= 31.1035 ÷ 11.664
1 Troy Pound (troy lb)
12 troy oz
= 373.24 g
1 Avoirdupois oz
28.3495 g
Common ounce — NOT used for gold
1 Kilogram
32.1507 oz t
= 1,000 ÷ 31.1035
1 Tola
0.3750 oz t
= 11.664 ÷ 31.1035
1 Gram
0.03215 oz t
= 1 ÷ 31.1035
The Troy System — Origins & History
The troy weight system was used in Troyes, a major medieval trading fair city in France, and was formally adopted by the English mint in 1527. The system persists today exclusively for precious metals (gold, silver, platinum) and gemstones, while all other commerce uses the avoirdupois system.
The troy pound contains 12 troy ounces (compared to 16 avoirdupois ounces in the common pound). This makes the troy ounce heavier than the avoirdupois ounce, even though the troy pound is lighter than the common pound.
Why the Troy Ounce Still Matters
Every gold price you see on financial terminals, commodity exchanges, and dealer websites is quoted in USD per troy ounce. When the news reports "gold hit $3,000 an ounce," that is a troy ounce. This matters practically because:
If a dealer quotes you a price "per ounce" without specifying troy, verify they mean troy — the price difference is about $500 at current rates.
Gold bar weights are given in troy ounces or grams. A "1-ounce gold coin" (like the American Eagle) always means 1 troy ounce = 31.1035 grams.
Converting local prices to per-gram requires dividing the spot price by 31.1035, not 28.35.
Other Gold Weight Units
While the troy ounce is the global benchmark, regional markets use other traditional units:
Tola — 11.664 grams. Used in India, Pakistan, UAE, and most Gulf countries. Equivalent to exactly ¾ of a tola = 1 troy ounce × 0.375.
Vori (Bhari) — 11.664 grams, identical to the tola. The standard unit in Bangladesh.
Baht Weight — 15.16 grams. The Thai gold standard, set by the Gold Traders Association of Thailand.
Masha — 0.972 grams. A sub-unit of the tola used in South Asian retail (12 masha = 1 tola).
One troy ounce equals exactly 31.1034768 grams. This is the universal standard unit for quoting gold prices globally. The troy ounce is approximately 10% heavier than the common avoirdupois ounce (28.3495 grams) used for everyday goods.
What is the difference between a troy ounce and a regular ounce?
A troy ounce (used for precious metals) = 31.1035 grams. A regular (avoirdupois) ounce (used for food, postal weights, etc.) = 28.3495 grams. The troy ounce is about 9.7% heavier. Never use a regular ounce to calculate gold — it will undervalue a piece by nearly 10%.
Why is gold measured in troy ounces?
The troy system originates from Troyes, a medieval French trading city, and was adopted by the English mint system in the 15th century. It became the global standard for precious metals through the British Empire's influence on international trade. The troy pound (12 troy ounces) was the UK monetary standard; the avoirdupois pound (16 oz) is used for general commerce.
How many troy ounces in 1 kilogram of gold?
There are 32.1507 troy ounces in 1 kilogram of gold (1,000 ÷ 31.1034768 = 32.1507 oz). A standard London Good Delivery gold bar weighs 400 troy ounces (12.44 kg), worth approximately $1.7 million at current prices.
How do I convert grams to troy ounces for gold?
Divide the weight in grams by 31.1034768 to get troy ounces. Example: 50 grams ÷ 31.1035 = 1.6075 troy ounces. Or use our gold price calculator which handles all unit conversions automatically.
