Bacteriostatic Water Calculator
Calculate how much bacteriostatic water you need for your peptide protocol. Add all your peptide vials and find out how many BAC water bottles to order.
Your peptide vials
What is bacteriostatic water?
Bacteriostatic water (BAC water) is sterile water that contains 0.9% benzyl alcohol as a preservative. The benzyl alcohol prevents bacteria from growing in the water, making it safe to use multiple times from the same vial over 28-30 days.
It is the standard diluent for reconstituting lyophilized (freeze-dried) peptides. Do not confuse it with sterile water for injection, which contains no preservative and must be used immediately after opening.
BAC water vs sterile water
| Feature | BAC Water | Sterile Water |
|---|---|---|
| Preservative | 0.9% benzyl alcohol | None |
| Multi-dose use | Yes (28-30 days) | No (single use) |
| Best for | Peptides you dose multiple times | Single-use reconstitution |
| Storage after opening | Room temperature, up to 28 days | Discard unused portion |
| Cost | $3-8 per 30 mL vial | $2-5 per vial |
How much BAC water per vial?
There is no single right answer. Common amounts are 1-3 mL per peptide vial. The amount only changes the concentration — not the total peptide. Here are the trade-offs:
- Less water (1 mL): Stronger concentration, smaller injection volume. Harder to measure precisely.
- Standard (2 mL): Good balance of concentration and measurability. Most common choice.
- More water (3 mL): Weaker concentration, larger injection volume. Easier to measure small doses.
Storage and shelf life
- Unopened BAC water: Store at room temperature. Check expiration date on vial.
- Opened BAC water: Use within 28 days. Store at room temperature away from direct light.
- Reconstituted peptide: Refrigerate at 2-8 degrees C. Use within 28-30 days.
FAQ
How many peptide vials can I reconstitute with one 30 mL BAC water bottle?
If you use 2 mL per peptide vial (the most common amount), a single 30 mL bottle of BAC water will reconstitute 15 peptide vials. Most people running 1-2 peptides need only one bottle per month.
Can I reuse BAC water after opening?
Yes. The benzyl alcohol preservative allows multi-dose use for up to 28 days after first puncture. Always use a new sterile needle each time you draw from the vial.
Where do I buy bacteriostatic water?
BAC water is available over the counter from most pharmacies, medical supply stores, and online retailers. It does not require a prescription. Typical cost is $3-8 per 30 mL vial.
Can I use saline instead of BAC water?
Bacteriostatic saline (0.9% NaCl with benzyl alcohol preservative) can be used for some peptides. However, plain normal saline without a preservative should not be used for multi-dose vials. When in doubt, use bacteriostatic water — it is the standard for peptide reconstitution.
Disclaimer: This calculator is for educational reference only. Always consult with a healthcare provider before using any peptide. See our full medical disclaimer.