Precious Metals Weight Converter
Convert between grams, pennyweights, troy ounces, and standard ounces. Plus reference guides for gold karats, platinum grades, and silver purities.
Weight Converter
Gold Karat Reference
| Karat | Purity % | Fineness |
|---|---|---|
| 24K | 99.9% | 999 |
| 22K | 91.67% | 916 |
| 18K | 75% | 750 |
| 14K | 58.3% | 585 |
| 10K | 41.7% | 417 |
| 9K | 37.5% | 375 |
European/UK jewelry uses fineness (parts per thousand). US jewelry uses karat. 750 = 18K, 585 = 14K, etc.
Platinum Grades
| Grade | Purity % | Notes |
|---|---|---|
| 950 Platinum | 95% | Standard fine jewelry grade |
| 900 Platinum | 90% | Often used in vintage pieces |
| 850 Platinum | 85% | More durable, some vintage jewelry |
| Iridium-Platinum | 90% | 90% Pt, 10% Ir - very hard |
Platinum stamps: "950 Pt", "Plat", "Pt900", "IRID PLAT". Palladium (Pd) is sometimes used as an alloy.
Silver Grades
| Grade | Purity % | Fineness |
|---|---|---|
| Fine Silver | 99.9% | 999 |
| Sterling Silver | 92.5% | 925 |
| Coin Silver | 90% | 900 |
| Britannia Silver | 95.84% | 958 |
Quick Reference: Conversion Factors
Troy Ounce (precious metals)
- • 1 troy oz = 31.1035 grams
- • 1 troy oz = 20 pennyweights
- • 1 troy oz ≠ 1 standard oz!
Pennyweight (dwt)
- • 1 dwt = 1.555 grams
- • 20 dwt = 1 troy oz
- • Used by US jewelers/dealers
⚠️ Standard ounces (avoirdupois) are used for everyday items. Precious metals use troy ounces—they're about 10% heavier.
Why Precious Metal Weights Are Different
If you've ever wondered why gold dealers talk about "troy ounces" instead of regular ounces, here's the short answer: precious metals have used the troy system since the Middle Ages, and it stuck.
Troy vs. Avoirdupois
A troy ounce weighs about 31.1 grams, while a standard (avoirdupois) ounce weighs about 28.35 grams. That ~10% difference matters when you're dealing with gold at $2,000+ per ounce. Always verify which system is being used.
Why Pennyweights?
American jewelers traditionally use pennyweights (dwt) because it's a convenient middle ground— not as small as grams, not as large as troy ounces. When you bring scrap gold to a buyer, they'll likely weigh it in pennyweights or grams.
Understanding Karats vs. Carats
Karat (with a K) measures gold purity. Carat (with a C) measures gemstone weight. Different words, different meanings—though they share an origin from the carob seed, historically used as a balance weight.
Related Guides & Resources
Ready to Browse Authenticated Pieces?
Every item at Spectra Fine Jewelry goes through our verification process before it hits the case. No guesswork. No surprises.