BAC Water Calculator for Peptide Reconstitution
BAC Water Calculator
Find how much bacteriostatic water to add for a target concentration.
Inputs
IU reference table
| Syringe | per 1 IU | per 10 IU | per 25 IU | per 50 IU |
|---|---|---|---|---|
| 1 mL / 100 IU | — | — | — | — |
| 0.5 mL / 50 IU | — | — | — | — |
| 0.3 mL / 30 IU | — | — | — | — |
Frequently Asked Questions
Q1What is bacteriostatic water and why is it used for peptides?
Bacteriostatic water (BW) is sterile water containing 0.9% benzyl alcohol, which inhibits bacterial growth and allows multi-dose use. It is the standard reconstitution solvent for lyophilized peptides because it keeps the vial sterile for up to 28 days after first puncture when refrigerated at 2–8 °C.
Q2How much bacteriostatic water should I add to a peptide vial?
The volume depends on your target concentration. A common approach is 1–2 mL of BW per 5 mg vial, giving 2,500–5,000 mcg/mL. Enter your vial amount and desired concentration into the BAC Water Calculator above to get the exact volume in mL and injection units.
Q3Can I use sterile water for injection instead of bacteriostatic water?
Plain sterile water for injection (SWFI) can reconstitute peptides but offers no antimicrobial protection. Once punctured, SWFI vials should be used within 24 hours. BW is preferred for multi-dose vials due to its benzyl alcohol preservative.
Q4How long does a reconstituted peptide vial last in the refrigerator?
Most peptides reconstituted in bacteriostatic water remain stable refrigerated (2–8 °C) for 4–6 weeks. Exposure to heat, light, or repeated freeze-thaw cycles accelerates degradation. Always store away from direct light and never freeze a reconstituted vial.
What This Calculator Does
The BAC Water Calculator works in reverse to the reconstitution calculator: you enter a desired concentration and vial size, and it tells you how much bacteriostatic water to add to hit exactly that concentration.
Formula Used
BAC Water (mL) = Vial Size (mg) × 1,000 ÷ Target Concentration (mcg/mL)Example Calculation
Limitations
Assumes 100% purity and complete dissolution. Higher concentrations (above 2,000 mcg/mL) may lead to stability issues with some peptides.