The fields you set on a custom product determine how the app values your inventory — both at the moment of purchase and every time spot prices refresh afterwards.
Getting them right is the difference between a Holdings page that mirrors reality and one that drifts off by a noticeable amount.
This article is the conceptual deep-dive on the three fields that drive the math: the calculation method itself, and the fields that change depending on which method you pick.
For the broader walkthrough of the custom product form (name, metal, form, notes), see Creating a custom product. This article zooms in on the math-driving fields.
The two calculation methods at a glance
Every custom product uses one of two methods to compute its melt value:
Standard: For any bullion product whose value scales directly with weight and a metal's spot price. This covers virtually everything: coins, bars, rounds, generic silver, refinery products, you name it.
Junk Silver: For fractional silver coinage that's valued by face value rather than weight. This is the method built-in for pre-1965 US fractional silver, and the one to use for non-US fractional silver as a custom product.
Standard is the default and what most custom products will use. Junk Silver is a specialised method for a specific kind of product. If you're not setting up fractional coinage that's bought and sold by face value, Standard is the right call.
Standard method
Two fields drive the math: Weight and Purity. Only one of them actually appears in the melt calculation.
Weight (troy oz) — enter the metal content
The weight field stores the pure metal content of the piece, in troy ounces — not the gross physical weight. For most modern bullion products, the pure metal content is the headline number printed on the product or in its marketing, so the field reads more naturally than it sounds.
A few examples to anchor what "metal content" means in practice:
10 oz silver bar (.999 fine). Weight = 10. The bar contains 10 troy oz of silver; the small amount of alloy in the .001 isn't material to the headline number.
1 oz American Silver Eagle (.999 fine). Weight = 1. The coin physically weighs about 1.001 oz including the trace alloy, but the headline content is 1 oz of silver.
1 oz American Gold Eagle (22 karat, .9167 fine). Weight = 1. The coin physically weighs about 1.0909 oz because of the copper alloy in 22 kt, but the headline content is 1 oz of gold. The extra copper isn't gold and isn't valued as gold.
50 g silver bar (.999 fine). Convert grams to troy ounces: 50 g ÷ 31.1035 ≈ 1.6075. The "50 g" branding is the headline silver content; the gross weight is essentially the same since the alloy fraction is tiny.
The convention matches the built-in catalog. If you flip through the Standard Catalog tab and look at the Weight column, every row stores the metal content, not the gross weight — that's why the 1 oz Gold Eagle and the 1 oz Silver Eagle both read as 1.0 despite physically weighing different amounts.
Purity (0–1) — the fineness, for display
The purity field stores the fineness of the alloy, expressed as a decimal between 0 and 1:
Fineness | Decimal | Where you'll see it |
Four-nines | 0.9999 | PAMP, Valcambi, most modern silver bars |
Three-nines | 0.999 | Generic silver rounds, Sunshine, Asahi |
Platinum bullion | 0.9995 | Platinum coins and bars |
22 karat | 0.9167 | American Eagles, Krugerrands |
90% silver | 0.900 | Pre-1965 US fractional |
Purity is display metadata. It appears in the Purity column on your Holdings page and on the catalog row for the product, but it doesn't multiply into the melt calculation directly. The reason: you've already entered the pure metal content in the Weight field, so the math doesn't need to multiply by purity a second time.
Stated as a formula, the Standard method is just:
melt value = weight × spot price
(Not weight × purity × spot. If purity were applied again, a 1 oz Gold Eagle would value at 1 × 0.9167 × $4,700 ≈ $4,308 — undercounting the gold by 8.33%. Storing the pure-metal weight up front avoids the double-discount.)
So: enter weight as pure metal content, enter purity as the fineness for display, and trust the rest.
Junk Silver method
Two different fields show up when you switch the toggle: Face Value / Unit and Silver Multiplier.
Face Value / Unit ($)
The face value of one coin, in whatever currency the coin was minted in. For US junk silver entries the unit is dollars — $0.10 for a dime, $0.25 for a quarter, $0.50 for a half dollar, $1.00 for a Morgan or Peace dollar. For non-US coins, enter the face value in the local currency unit at the time the coin was struck (a pre-1947 British shilling has face value 0.05 pounds, a pre-1967 Canadian dime has face value 0.10 Canadian dollars, and so on).
The field is named in dollars in the UI for simplicity, but the math is currency-agnostic — the multiplier does the work of converting face value into a silver content figure, and the silver content gets valued against US spot at the end.
Silver Multiplier
The number of troy ounces of pure silver contained in one unit of face value. The two common US values are pre-baked into the catalog, but for custom non-US setups, you'll need the multiplier for that particular coinage:
0.715: 90% US silver (and a few other 90% national coinages of similar weight standards)
0.295: 40% Kennedy half dollars (1965–1970)
0.600: 80% Canadian silver (pre-1967 dimes, quarters, halves)
0.400: 50% Canadian silver (1967–1968 dimes and quarters of mixed composition)
0.654: 92.5% sterling British pre-1920 silver (sixpence, shilling, florin, half crown, crown)
0.354: 50% British silver (1920–1946)
Plug in the multiplier and the math runs as:
melt value = face value × multiplier × spot price
A worked example for non-US junk silver: a pre-1967 Canadian dime ($0.10 face, 0.600 multiplier) at $80 silver melts at 0.10 × 0.600 × $80 = $4.80 per coin. A pre-1920 British shilling (£0.05 face value, 0.654 multiplier) at $80 silver melts at 0.05 × 0.654 × $80 = $2.62 per coin.
For a deeper walk-through of the Junk Silver calculation, see How junk silver melt value is calculated and Custom junk-silver-style products.
When to use each method
The decision tree is short:
The product is bought and sold by weight (the typical bullion case — any coin, bar, or round priced over spot) → Standard.
The product is fractional coinage bought and sold by face value (any "junk silver" pattern, US or otherwise) → Junk Silver.
If you're holding a non-US silver bullion coin — a Chinese Silver Panda, a Russian St. George — that's still Standard. The Junk Silver method is specifically for circulating fractional silver coinage where face value drives the trade.
A custom product can't switch calculation methods after the fact. If you set up something as Standard and realise it should have been Junk Silver, the cleanest path is to deactivate the original and create a new one with the right method.
Where to go next
Creating a custom product: The broader form walkthrough, with Name, Metal, Form, and Notes.
How junk silver melt value is calculated: The math in plain English.
Understanding melt value: The Standard melt formula in plain English.
Editing or deactivating a custom product: How to adjust a custom product after the fact.