Gold jewelry, scrap and dental gold are sold by weight and karat. This calculator converts a weight in grams, pennyweight, troy ounces, grains or kilograms into the weight of pure gold it contains, and, if you add a price you got from a live quote, the metal value.
Your weight, all units: —. Metal value is what the gold is worth by weight, not what a buyer will pay: refiners and dealers pay a share of it, and stones, clasps and solder are not gold.
How the arithmetic works
Karat is a count of 24ths. Pure gold is 24 karat (the FTC’s Jewelry Guides call “fine (24 karat) gold” the unalloyed metal[11]), so 18K is 18/24 = 75% gold and 14K is 14/24 = 58.3% gold. Multiply the item’s weight by that fraction and you have the weight of pure gold. Divide by 31.1035 and you have troy ounces, the unit gold is quoted in.
| Karat | Gold share | Fineness (parts per 1,000) |
|---|---|---|
| 24K | 100.00% | 1000 |
| 22K | 91.67% | 917 |
| 21K | 87.50% | 875 |
| 18K | 75.00% | 750 |
| 14K | 58.33% | 583 |
| 12K | 50.00% | 500 |
| 10K | 41.67% | 417 |
| 9K | 37.50% | 375 |
| 8K | 33.33% | 333 |
Weights people mix up
- Troy ounce = 31.1035 g. This is the ounce for gold, silver and platinum. An everyday (avoirdupois) ounce is 28.35 g, so weighing a ring on a kitchen scale set to ounces understates the gold.
- Pennyweight (dwt) = 1/20 troy ounce = 1.5552 g. Jewelers and refiners still quote it.
- Grain = 0.0648 g. Old coin laws, such as the 1837 Coinage Act, define coin weights in grains; there are 480 grains in a troy ounce.
Before you sell scrap gold
- Get at least three written offers, and ask each buyer what percentage of metal value it represents.
- Check the karat stamp. A “14K” or “585” mark means 58.5% gold; a missing stamp means the item needs testing.
- Never ship items before you have the buyer’s terms in writing.
Also see: the coin melt value calculator and the coin content chart.
Sources
- 16 CFR §23.3 (FTC Jewelry Guides): fine gold is 24 karat; lower karat figures describe alloys — https://www.law.cornell.edu/cfr/text/16/23.3