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How Price per mg Is Computed, and Why Raw Vial Prices Mislead

Published

Listings for the same compound rarely come in the same size. One seller may list a 5 mg vial, another a 10 mg vial, and a third a bottle of capsules. Comparing the headline prices of these packs says little on its own. This index therefore expresses every listing as a price per milligram (USD per mg), calculated from the listed pack price and the stated pack content.

All numbers below are illustrative, for arithmetic demonstration only. They do not describe any real product, seller or market price, and no particular compound is meant.

The formula

For each listing the index records the price of the whole pack exactly as displayed, its currency, the content of one unit, the unit of measure, and the number of units in the pack. From these it computes:

  1. Total content in mg = unit amount x unit factor x number of units. The unit factors are: 1 mcg = 0.001 mg, 1 mg = 1 mg, 1 g = 1000 mg.
  2. Price in USD = listed price x the stored exchange rate for that currency (1 for USD).
  3. USD per mg = price in USD / total content in mg, rounded half up to six decimal places.

On the page, a value of 1 or more is shown with two decimals (such as $4.50/mg) and a value below 1 is shown with four decimals (such as $0.1200/mg).

Illustration 1: a larger vial with a higher price

  • Listing A: 1 vial, 5 mg, listed at 30.00 USD. Total content 5 mg, which gives 6.000000 USD per mg.
  • Listing B: 1 vial, 10 mg, listed at 45.00 USD. Total content 10 mg, which gives 4.500000 USD per mg.

Listing B has the higher pack price, yet it works out lower per milligram. Looking only at the 30.00 versus 45.00 headline would give the opposite impression. This is the main reason raw vial prices are a poor basis for comparison: the price of a pack scales with its content, and pack sizes vary from listing to listing.

Illustration 2: units other than mg

Some listings state content in micrograms or grams. A bottle of 60 capsules at 250 mcg each, listed at 39.00 USD, contains 60 x 250 x 0.001 = 15 mg, which gives 2.600000 USD per mg (shown as $2.60/mg). A 1 g pack of powder listed at 120.00 USD contains 1000 mg, which gives 0.120000 USD per mg (shown as $0.1200/mg).

The number of units matters. If the capsule count were missing and the bottle price were read as the price of a single 250 mcg capsule, the result would be 60 times too high. Listings without a clear unit count are therefore left out or deferred rather than estimated.

Illustration 3: a price in another currency

Suppose a listing shows 20.00 GBP for a 5 mg vial, and the stored rate in this illustration is 1 GBP = 1.30 USD. The price in USD is 26.00, and the result is 5.200000 USD per mg. The original price and currency stay on the listing, together with the rate used. A later change to the stored rate affects later imports only.

Comparisons happen within a form

The index groups listings by compound and form (vial, capsule, liquid, powder and a small number of other form labels). The capsule illustration above is compared with other capsule listings, not with vials. The minimum listed price and the median are calculated per group and only from listings marked in stock; out-of-stock listings remain visible but are left out of these figures.

What the number does not include

The per-mg figure is calculated from the listed pack price alone. It does not reflect shipping charges, payment fees, voucher codes or minimum order rules, and it says nothing about the content or quality of a product. It is a normalised view of listed prices, intended to make listings of different sizes readable side by side.