💧 BAC Water Optimizer
Enter your vial size, target dose, and desired draw units — the optimizer calculates the exact bacteriostatic water volume to add for a precise, easy-to-measure injection every time.
Reverse-Calculate Your Ideal Reconstitution Volume
Most reconstitution calculators work forward: you enter your BAC water volume and get a concentration. This tool works in reverse — you tell it your target dose and the exact number of syringe units you want to draw, and it tells you precisely how much bacteriostatic water to add to achieve that result. This is especially useful when you want to standardise your draw to a memorable unit mark (like exactly 10, 20, or 50 units), or when switching vial sizes without changing your syringe routine.
The tool also generates a sensitivity table showing how different target draw units correspond to different BAC water volumes, so you can choose the combination that best suits your syringe and accuracy requirements.
You want to draw exactly 20 units on a 0.5 mL syringe for a 500 mcg dose from a 5 mg vial.
- Required concentration = 500 × 100 ÷ 20 = 2,500 mcg/mL
- BAC water = (5 × 1,000) ÷ 2,500 = 2.0 mL
- Verify: 500 ÷ 2,500 = 0.20 mL = 20 units ✓
Peptide vial size
Dose per injection
Target draw (units on syringe)
Syringe volume
All values below are for your current vial size and dose. The highlighted row matches your target draw. Larger draws are more accurate; draws under 10 units have higher relative measurement error.
| Target Draw | BAC Water | Concentration | Accuracy |
|---|---|---|---|
| Select your inputs above to generate the table. | |||
BAC Water Optimizer — Frequently Asked Questions
Why does draw volume accuracy matter so much for small doses?
On a U-100 insulin syringe, each unit mark represents 0.01 mL. If you're drawing 10 units (0.10 mL) for a 500 mcg dose and misread by 1 unit, you're making a 10% dosing error — administering 450 mcg or 550 mcg instead of 500 mcg. That same 1-unit error on a 20-unit draw (0.20 mL) is only a 5% error. Drawing 40+ units reduces this further to 2.5% or less. The BAC Water Optimizer helps you find a reconstitution volume that produces a comfortable, accurate draw for your specific dose and syringe.
What is bacteriostatic water and why must I use it — not plain water?
Bacteriostatic water (BAC water) is sterile water for injection preserved with 0.9% benzyl alcohol. The benzyl alcohol acts as a bacteriostat — it inhibits bacterial growth, extending the stability of the reconstituted peptide solution to approximately 28 days when refrigerated. Plain sterile water for injection (WFI) contains no preservative, so once a vial is opened and peptide dissolved, bacterial contamination risk rises rapidly. A reconstituted peptide in plain WFI should be used within 24 hours. Always verify "bacteriostatic" on the label before use.
Can I add more BAC water later if I want a different concentration?
Yes — if you've already reconstituted a vial and want a lower concentration, you can carefully add more BAC water to dilute. The 28-day stability clock continues from the original reconstitution date, not the dilution date. You cannot increase concentration once diluted (without evaporation, which is not a safe method). For this reason, many researchers err on the side of less BAC water initially (higher concentration) knowing they can dilute later if the draw volume turns out impractically small.