Peptide calculator: vial size to concentration
Enter the amount of peptide in the vial and the volume of bacteriostatic water added. The calculator returns the concentration in mg/mL and mcg/mL, which is the figure a laboratory records alongside the batch number.
What reconstitution actually is
A lyophilised peptide is a dry powder that has been freeze-dried under vacuum. Reconstitution is adding a measured volume of sterile diluent, usually bacteriostatic water, to return it to solution. Bacteriostatic water contains 0.9% benzyl alcohol as a preservative, which is what distinguishes it from plain sterile water and allows a vial to be entered more than once.
The calculation
Concentration is the mass of peptide divided by the volume of diluent. A 10 mg vial with 2 mL of bacteriostatic water added gives 5 mg/mL, or 5,000 mcg/mL. The volume of the dry powder itself is small enough to ignore at these quantities, which is why the figure is taken as the diluent volume rather than the final solution volume.
Why more diluent is not automatically better
A larger volume gives a lower concentration and a more dilute solution, which is easier to measure accurately but fills the vial faster and leaves less headroom. A smaller volume concentrates the peptide, which suits small working amounts but makes any measurement error proportionally larger. Most laboratory protocols settle between 1 and 3 mL for a standard vial for exactly that reason.
What this calculator does not do
It stops at concentration. It does not convert into syringe markings, insulin units or an amount to administer, and it does not suggest how much to use. Those are dosing questions, and nothing on this site is supplied for use in a person. Health Canada stated in April 2026 that a "Research Use Only" label does not make a product legal to use in a person, and a supplier publishing a dosing tool beside that disclaimer is not taking it seriously.
Recording the result
Write the concentration, the diluent volume and the date mixed next to the batch number from the vial. That pairing is what lets an observation be traced back to the exact material that produced it, and it is the single most useful thing to record at this stage. Reconstituted material keeps far less well than the dry powder, so the date matters as much as the number.
Questions
How do I calculate peptide concentration?
Divide the mass of peptide in the vial by the volume of diluent added. A 10 mg vial with 2 mL of bacteriostatic water is 10 ÷ 2 = 5 mg/mL. Multiply by 1,000 for mcg/mL, so the same vial is 5,000 mcg/mL.
How much bacteriostatic water should I add to a vial?
That depends on the concentration a protocol calls for, and it is a decision about experimental design rather than something a supplier can set. The calculator shows what any volume produces so the figure can be chosen deliberately. Between 1 and 3 mL is common for a standard vial.
What is the difference between bacteriostatic water and sterile water?
Sterile water has no preservative, so a vial is single-use. Bacteriostatic water contains 0.9% benzyl alcohol, which inhibits bacterial growth and allows repeated withdrawal from the same vial.
Does the calculator give me a dose?
No. It converts vial size and diluent volume into concentration and stops there. It does not convert into syringe units and makes no recommendation about amounts.
How long does reconstituted peptide last?
Far less time than the dry powder, and it must be kept refrigerated. The exact figure depends on the compound and the conditions, so record the date you mixed it alongside the batch number rather than relying on a general rule.
Which products need reconstituting?
Only the lyophilised vials, which arrive as a dry powder. Nasal sprays ship as a finished solution and capsules are a dry oral format, so neither takes any liquid.