Methodology

Coin specifications

Coin weights and compositions come from US Mint coin specifications and the Coinage Acts of 1873 (17 Stat. 424) and 1965 (Public Law 89-81). For foreign coins, we use each issuing mint's official specifications. We record a sourceUrl for every coin in our dataset.

Melt value formula

For each metal in a coin:

Metal value = metal_content_troy_oz × spot_price_per_troy_oz

For copper (quoted per pound):

Metal value = metal_content_pounds × spot_price_per_pound

Total melt value is the sum of all metal values in the coin.

Weight conversions

We use the NIST-defined constants (NIST SP 811):

• 1 troy ounce = 31.1035 grams (exact)
• 1 troy ounce = 20 pennyweight (dwt)
• 1 troy ounce = 1.09714 avoirdupois ounces
• 1 avoirdupois pound = 453.592 grams

All precious metal spot prices are quoted in troy ounces. We never use avoirdupois ounces for precious metal calculations without explicitly converting.

Silver content calculation for constitutional silver

For 90% silver US coins:

• Dime (1916–1964): 2.5 g × 0.900 ÷ 31.1035 = 0.0723 ozt Ag
• Quarter (1932–1964): 6.25 g × 0.900 ÷ 31.1035 = 0.1808 ozt Ag
• Half dollar (90%): 12.5 g × 0.900 ÷ 31.1035 = 0.3617 ozt Ag
• Dollar (Morgan/Peace): 26.73 g × 0.900 ÷ 31.1035 = 0.7734 ozt Ag

Per $1 face value of 90% silver coins: 0.7234 ozt (theoretical new-coin weight). The industry convention of 0.715 ozt accounts for typical wear in circulated coins.

Spot price sourcing

Live spot prices are fetched client-side from gold-api.com, a free, CORS-enabled precious metals API requiring no API key. Symbols:

• XAG — Silver per troy oz
• XAU — Gold per troy oz
• XPT — Platinum per troy oz
• XPD — Palladium per troy oz
• HG — Copper per pound (avoirdupois)

Prices are cached in your browser's localStorage for 10 minutes to avoid excessive API calls. If the live fetch fails, calculators fall back to a build-time snapshot stored in src/data/spot-snapshot.json (refreshed when the site is rebuilt). The snapshot date is shown on the calculator when the fallback is active.

Nickel and zinc have no available free live price source. These calculators use stated manual defaults based on LME reference prices, displayed clearly with a date, and are always editable by the user.

Manual price overrides

Every price field on every calculator is editable. If you want to calculate at a historical price, a dealer-quoted price, or any other price, just type it in. The calculator recalculates immediately.

Limitations

• Wear reduces weight. Circulated coins weigh slightly less than their mint specification. A heavily worn Morgan dollar may yield 2–3% less silver than the theoretical 0.7734 ozt. Melt values for circulated coins are slight overestimates.
• Numismatic value is ignored. Melt value is a floor — collector coins, key dates, and high-grade coins can sell for multiples of melt. This calculator does not estimate numismatic value.
• Spot prices lag market close. The API may reflect the last traded price, which may differ from the official PM fix or next day's open. For large transactions, verify against a professional data source.
• Foreign coin data. Foreign coin specifications are sourced from each issuing mint where possible. Verify before transacting.