Comparing two peptide products on vial price tells you almost nothing. A 10 mg vial costs more than a 5 mg vial and may still be cheaper per dose. This post explains what cost per dose actually computes, what it excludes, and why the comparison most people make first is the wrong one.
The problem with comparing vial prices
Price per vial is a packaging decision, not a material property. A supplier can put the same peptide in a 5 mg vial or a 20 mg vial and adjust the price to suit their margins. Comparing the numbers on the labels compares packaging.
Cost per dose removes the packaging. It is the vial price divided by the number of doses that vial yields, and it depends on the amount per vial rather than on the size of the container.
The calculation
Three steps, and only the first involves the product:
doses per vial = vial mass / amount per dose
cost per dose = vial price / doses per vial
cost per week = cost per dose x doses per week
cost per month = cost per week x 4.345Worked, with invented figures: a 60 unit vial containing 5 mg, at 0.25 mg per dose.
doses per vial = 5 mg / 0.25 mg = 20
cost per dose = 60 / 20 = 3The 4.345 in the monthly figure matters. A month is not exactly four weeks; it is 365/84, so using 4 understates a monthly cost by about eight percent, which is enough to flip a comparison between two products.
The cost calculator does all of this and also reports how many days a vial lasts at the entered frequency.
Cost per milligram is not comparable across peptides
Cost per milligram is correct within one substance and misleading across substances, because different peptides weigh differently per molecule. A milligram of a 4000 g/mol peptide contains fewer molecules than a milligram of a 1000 g/mol peptide, so a milligram-for-milligram comparison flatters the heavier peptide by a factor of four.
The comparable unit is cost per micromole, which counts molecules rather than mass. Two micromoles of any two substances are the same number of molecules, so the comparison is like for like. The cost per micromole calculator does that conversion, and it needs the molecular weight because that is the number that relates mass to molecules.
What cost per dose leaves out
This is the part worth reading twice, because the exclusions are often larger than the vial price itself:
- Shipping and duties. Frequently a significant fraction of the total, and never included in a advertised vial price.
- Consumables. Diluent, syringes, needles, filters and tips. The batch cost calculator exists because a real project total usually has more rows for these than for the peptide.
- Wastage. A reconstituted vial has a limited usable life, and material left in a filter or a vial wall is lost. Real doses per vial are lower than the theoretical count.
- Failed attempts. If a synthesis or an order took two tries, that is twice the cost for one success.
- Your time. Not invoiced, and not free.
A vial price of 60 with consumables and shipping of 30 is a cost per dose of 4.5, not 3. The arithmetic is exact either way; what it covers is the question.
What this site does not do
The calculators here price arithmetic. They do not compare quality, purity, stability, storage requirements or suitability, and a cheaper cost per dose is not a better product. Nothing here recommends a product, an amount or a frequency.
Related: the cost per milligram calculator and inventory and days remaining.