How to calculate bullion premium over spot
The one formula that turns any dealer price into an apples-to-apples number you can compare.
The premium over spot is simple once every price is on a per-ounce basis. The formula:
premium % = (price per troy oz − spot) ÷ spot × 100
The only trick is converting the item to a per-troy-ounce price first— because a 1/10 oz coin, a 1 oz round, and a 100 gram bar can't be compared until they're on the same scale. Here's the four-step method, then worked examples for coins, fractional pieces, and grams.
The four steps
- 1. Get the current spot price per troy ounce for the metal.
- 2. Convert the item to a price per troy ounce: divide the total price by the item's weight in troy ounces. (For grams, divide by grams, then multiply by 31.1035.)
- 3. Dollar premium = price per oz − spot.
- 4. Percentage premium = dollar premium ÷ spot × 100.
Worked examples
A 1 oz gold coin. Spot $4,000. Coin price $4,180.
- Per oz = $4,180 ÷ 1 = $4,180.
- Dollar premium = $4,180 − $4,000 = $180.
- Percentage = 180 ÷ 4,000 × 100 = 4.5% over spot.
A 1/10 oz gold coin. Spot $4,000. Coin price $460.
- Per oz = $460 ÷ 0.1 = $4,600.
- Dollar premium = $4,600 − $4,000 = $600 per ounce.
- Percentage = 600 ÷ 4,000 × 100 = 15% over spot — the small piece is far pricier per ounce, even though its sticker looks cheap.
A 100 gram silver bar. Spot $30/oz. Bar price $110.
- Weight in troy oz = 100 ÷ 31.1035 = 3.215 oz.
- Per oz = $110 ÷ 3.215 = $34.22.
- Percentage = (34.22 − 30) ÷ 30 × 100 = 14% over spot.
That per-ounce step is the whole game: it's why a “cheap” fractional coin can be the most expensive silver or gold you can buy, and why bars priced in grams need a quick conversion before you judge them.
See it computed live
StackerSpot runs this math on every listing automatically and normalizes each to a per-troy-ounce basis, so the premiums are directly comparable across forms and weights:
A couple of gotchas
- Pack pricing. A tube or box price is for the whole lot — divide by the count and the unit weight before you compute a per-ounce number.
- Cash vs card. Decide which price basis you're using and stay consistent; card typically runs a few percent above the advertised cash/wire figure.
- Spot moves. Premium is only meaningful against a current spot price — a stale spot makes the percentage wrong.
Skip the math — see live premiums
Every product normalized per ounce and ranked by premium over spot.
Common questions
How do I convert grams to troy ounces?
One troy ounce is 31.1035 grams. To get a per-troy-ounce price, divide the item's price by its weight in grams, then multiply by 31.1035. For example, a 20 g bar at $2,600 is $130/g × 31.1035 = about $4,043 per troy ounce.
What's the difference between the dollar premium and the percentage premium?
The dollar premium is how many dollars over spot you pay per ounce; the percentage premium expresses that as a share of spot. Percentage is what makes different products comparable — a $150 premium is small on a $4,000 ounce of gold (about 3.8%) but enormous on a $30 ounce of silver.
Does StackerSpot calculate the premium for me?
Yes. StackerSpot converts every dealer listing to a per-troy-ounce basis and computes the premium over live spot automatically, so you can compare a 1/10 oz coin, a 1 oz round, and a 100 g bar on the same scale without doing the math yourself.
Should I use the cash price or the card price when I calculate?
Be consistent and know which basis you're using. Most dealers advertise the cash/wire price; paying by credit card typically adds a few percent. StackerSpot uses the cash/wire basis, so compare like with like — and add the card surcharge if that's how you'll pay.
Methodology & sources
StackerSpot computes premiums live on a per-troy-ounce, cash/wire basis against current spot — the same math shown here — detailed in our methodology. One troy ounce = 31.1035 grams (standard market convention). Worked examples use round hypothetical numbers. Next, read how much over spot you should pay.
Informational purposes only — not investment, financial, or tax advice, and not a licensed dealer or advisor. Prices are each dealer's cash/wire figure, change constantly, and may differ from the dealer's own site; always confirm before buying. See our methodology & disclaimer.