Gold Karats, Troy Ounces, and Jewelry Melt Value: How to Calculate
October 29, 2026
Precious metals are priced per troy ounce, a unit of mass used in the precious metals trade that is about 10% heavier than the common avoirdupois ounce: 1 troy ounce = 31.1035 grams, whereas 1 ordinary ounce = 28.3495 grams. Gold jewelry is rarely pure gold; it is alloyed with other metals for hardness and color. The purity is stated in karats (k), where 24 karats is pure gold. The fraction of pure gold is karats ÷ 24.
So 18k gold is 18/24 = 75% gold, 14k is 58.3%, 10k is 41.7%. A 10-gram, 14-karat ring contains 10 × 14/24 = 5.83 grams of gold, which is 5.83 ÷ 31.1035 = 0.1875 troy ounces.
Skip the math and get your answer instantly:
Open the Weight Converter →Melt Value Formula
Melt value = weight in grams × (karats ÷ 24) ÷ 31.1035 × spot price per troy ounce. The spot price changes constantly; this article uses an illustrative price of $2,500 per troy ounce. For the 10 g 14k ring: 0.1875 oz × $2,500 = $468.86. For a 10 g 18k pendant: 7.5 g of gold = 0.2411 oz × $2,500 = $602.83. For a 10 g 10k bracelet: 4.17 g = 0.1340 oz = $334.90. Pure 24k bullion: 10 g = 0.3215 oz = $803.77. Check the current spot price before any transaction, and weigh the item on an accurate scale in grams.
Weights of stones and non-gold parts should be subtracted. Dealers weigh the metal only.
| Purity | Gold fraction | Pure gold in 10 g | Melt value at $2,500/oz (illustrative) |
|---|---|---|---|
| 24k | 99.9% | 10.0 g | $803.77 |
| 22k | 91.7% | 9.17 g | $736.80 |
| 18k | 75.0% | 7.50 g | $602.83 |
| 14k | 58.3% | 5.83 g | $468.86 |
| 10k | 41.7% | 4.17 g | $334.90 |
Hallmarks and Verification
Look for stamps indicating purity: 750 or 18K for 75%, 585 or 14K for 58.5%, 417 or 10K, 999 for pure. Some items are gold-plated or gold-filled and have far less gold; markings like GP, GF, or GEP indicate this. A magnet will not attract real gold, but this test alone is not conclusive. Acid tests, electronic testers, and X-ray fluorescence (XRF) analyzers used by jewelers and buyers can verify purity. Be careful when buying or selling, and get quotes from more than one reputable dealer.
Why You Won't Get Melt Value
Buyers pay less than melt value for scrap gold because they must cover refining costs and margin, typically offering 70% to 90% of melt value depending on the buyer and quantity. Jewelry retail prices include design, labor, brand, and markup, often far above the metal value. Gold coins and bars trade at a premium over spot to cover minting and distribution. Collectible or antique pieces may be worth more than their melt value. If you are selling, get multiple offers, understand the gram weight and purity, and be aware of local rules on record keeping.
Troy vs. Avoirdupois
There are 12 troy ounces in a troy pound (373.24 g), versus 16 avoirdupois ounces in a pound (453.59 g). A troy ounce is 480 grains, while an avoirdupois ounce is 437.5 grains. Gems are measured in carats (1 carat = 0.2 g), which should not be confused with karats for gold purity. Platinum and silver are also quoted per troy ounce. When comparing prices in grams, divide the per-ounce price by 31.1035: $2,500 per ounce is $80.38 per gram.
Frequently Asked Questions
How many grams are in a troy ounce?
31.1035 grams.
What percentage of gold is 14 karat?
58.3%, or 14/24.
How do I calculate the melt value of gold jewelry?
Multiply the grams by the gold fraction, divide by 31.1035, and multiply by the spot price per troy ounce.
What is the difference between carat and karat?
Carat measures the weight of gems, and karat measures gold purity.
Why do buyers pay less than melt value?
To cover refining costs and their margin.