← Full peptide calculator
Free tool
This free bacteriostatic water calculator works out the concentration of a reconstituted peptide vial — and how much bacteriostatic water to add to reach a target concentration. Enter your vial strength in milligrams and the BAC water volume to get mg/mL, or enter a target concentration to get the water to add. Arithmetic only — not medical advice.
Concentration = vial mg ÷ water mL. Arithmetic only — not medical advice; verify against the product label and with a clinician.
Frequently asked questions
What is bacteriostatic water?
Bacteriostatic water is sterile water with a small amount of benzyl alcohol (commonly about 0.9%) that inhibits bacterial growth, which is what lets a reconstituted vial be drawn from more than once. This calculator only works in millilitres of whatever diluent you enter — it does not choose a diluent for you. Always follow the product label and a pharmacist or clinician.
How much bacteriostatic water should I add?
There is no single correct amount. More water gives a larger, easier-to-measure draw volume but a more dilute solution; less water concentrates it. Enter the volume you plan to use and the calculator shows the resulting concentration in mg/mL, so you can pick a ratio that lands on clean, readable syringe marks.
How does it work out the concentration?
Concentration is simply the peptide mass divided by the liquid volume: mg ÷ mL = mg/mL. Enter the vial strength in milligrams and the water in millilitres and it returns the concentration; enter a target concentration instead and it returns the water to add. It is arithmetic only.
Can I use sterile or plain water instead?
This tool only performs the arithmetic — it does not assess which diluent is appropriate, sterility, or stability. Confirm the correct diluent and handling with the product label, a pharmacist, or a clinician before any use.
Is this calculator medical advice?
No. It is an arithmetic and reference tool only. It does not recommend a dose, a product, or a diluent, and it does not assess whether anything is appropriate for you. Always verify with a clinician, the product label, or a pharmacist.