Table of Contents
Gold Weight Units
Gold is traditionally weighed using the troy weight system, not the avoirdupois system used for everyday items. A troy ounce equals 31.1035 grams, about 10% heavier than a standard (avoirdupois) ounce of 28.3495 grams. This distinction is critical for accurate gold valuation and trading.
Other units used in the gold trade include pennyweight (dwt), equal to 1/20 of a troy ounce or 1.555 grams, commonly used by jewelers. The metric system (grams and kilograms) is increasingly used in international gold markets. Gold purity is measured in karats (parts per 24) or fineness (parts per 1000).
Conversion Formulas
Karat Purity Chart
| Karat | Purity % | Fineness | Common Use |
|---|---|---|---|
| 24K | 99.9% | 999 | Bullion, coins |
| 22K | 91.6% | 916 | High-end jewelry |
| 18K | 75.0% | 750 | Fine jewelry |
| 14K | 58.5% | 585 | Standard jewelry |
| 10K | 41.7% | 417 | Affordable jewelry |
Frequently Asked Questions
Why is gold weighed in troy ounces?
The troy weight system has been used for precious metals since medieval times, originating from the French city of Troyes. It persists because the global gold market is standardized around troy ounces, and changing would cause enormous confusion. The London Bullion Market Association and COMEX both price gold per troy ounce.
What is melt value vs market value?
Melt value is the worth of the pure gold content at current spot prices. Market value includes premiums for craftsmanship, rarity, brand, and condition. Gold jewelry typically sells for 70-95% of melt value when sold to dealers, while rare coins or designer pieces may sell for multiples of melt value to collectors.