How the calculators work
Melt value is the pure metal times the spot price. This page is the method behind every calculator on the site.
Updated
The melt formula
Melt value is grams × (karat ÷ 24) × (spot per troy ounce ÷ 31.1034768). One troy ounce is 31.1034768 grams. One pennyweight is 1.55517384 grams. One regular ounce is 28.349523125 grams. The regular ounce is the kitchen ounce, and it is lighter than a troy ounce.
Purity
Karat divided by 24 is the gold fraction this site uses. A 585 stamp is 58.5 percent, which is a hair above 14 ÷ 24. The karat pages say so beside the result.
| Karat | Percent | Fineness |
|---|---|---|
| 24K | 100% | 1000 |
| 22K | 91.7% | 917 |
| 21K | 87.5% | 875 |
| 18K | 75% | 750 |
| 14K | 58.3% | 583 |
| 12K | 50% | 500 |
| 10K | 41.7% | 417 |
| 9K | 37.5% | 375 |
| 8K | 33.3% | 333 |
A purity you type
Custom purity follows one rule. A number up to 100 is a percent, so 40 means 40 percent. A number from 101 to 1,000 is fineness out of 1,000, so 585 means 58.5 percent. The dental calculator starts with an empty purity box because a crown has no default karat.
Where the price comes from
The browser asks this site for /api/spot when a calculator loads, then again about once a minute. The server asks gold-api.com for gold and, when it can, for silver, and it reuses a gold quote for about 45 seconds. Exchange rates come from ExchangeRate-API and are reused for about 12 hours. A live quote is labelled Live. If the feed does not answer, the box shows the sample price from the site settings and the badge says Sample. A number you type is labelled Custom and stays until you reset it. Silver uses the same three labels. If the response has no silver price, silver stays on its sample figure.
Rounding
Dollar lines use the usual minor units for the currency you pick: two for US dollars. Weights on each calculator are rounded for display after the full factor is applied. A one-ounce Eagle uses its published actual gold weight, not a rounded fineness times a rounded gross weight.
Buyer ranges
The scrap calculator shows these bands as a share of melt. They are estimates of what buyers often pay, not a quote from any shop.
| Buyer | Share of melt |
|---|---|
| Mail-in refiner | 85–95% |
| Local jeweler | 65–80% |
| Pawn shop | 50–70% |
Who checks this page
Richard Hollis is assigned to the maths and the market context. Helen Brandt is assigned to purity and hallmark wording, and to the rule that an estimate is never called an appraisal. Their names appear in the byline only after each review is confirmed.
What the estimate leaves out
Stones, enamel, cement, steel posts and a worn or holed coin are not in the formula. Gold-filled scrap uses the stamped ratio, which is a small share of the weight. Dental gold can contain platinum-group metals that this site does not price. A collector coin can be worth more than melt, and a dealer can pay less. The price can be delayed, or it can be the sample figure.
Versions
| Date | What changed |
|---|---|
| 2026-11-09 | Scrap, karat, weight, gold-filled, dental, coin, and gold-and-silver calculators, with this methodology page. |