🧪 Reconstitution Calculator
Calculate solution concentration after adding BAC water — includes a complete dosing table and BAC water optimizer.
How Reconstitution Works
Peptides are sold as lyophilised (freeze-dried) powder and must be reconstituted with bacteriostatic water (BAC water) before injection. The amount of BAC water you add determines your solution concentration — and concentration controls exactly how many units to draw on your syringe for every single dose. Getting this wrong causes direct under- or over-dosing, which is why this step must be calculated precisely.
This calculator handles the maths instantly, generates a complete dosing table, flags any draw volumes too small to measure accurately on a standard insulin syringe, and optimises your BAC water amount for a comfortable 0.2 mL (20-unit) injection.
You have a 5 mg BPC-157 vial and add 2 mL BAC water. You want a 500 mcg dose on a U-100 syringe.
- Concentration = (5 × 1,000) ÷ 2 = 2,500 mcg/mL
- Volume for 500 mcg = 500 ÷ 2,500 = 0.2 mL
- On U-100: 0.2 × 100 = draw to the 20-unit mark
- On U-40: 0.2 × 40 = draw to the 8-unit mark
Reconstitution Calculator
Enter your vial size and the amount of BAC water you plan to add. Results update in real time.
For a comfortable 0.2 mL (20 units) at your target dose, add this much BAC water:
| Dose | Volume (mL) | Units to draw | Accuracy |
|---|
Rows marked ⚠ have volumes too small to draw reliably — use the BAC optimizer above to fix this.
Reconstitution — Frequently Asked Questions
What is bacteriostatic water and why must I use it?
Bacteriostatic water (BAC water) is sterile water containing 0.9% benzyl alcohol as a preservative. Unlike plain sterile water, BAC water inhibits bacterial growth — which is critical because a reconstituted vial is pierced multiple times over its 28-day use period. Using plain water creates a contamination risk with every injection. BAC water also maintains the structural integrity of most peptides better than alternative solvents. It is the correct diluent for the vast majority of research peptides including BPC-157, TB-500, CJC-1295, and all GHRPs.
How much BAC water should I add to my vial?
The ideal amount depends on your dose. The goal is to produce an injection volume of 0.1–0.3 mL (10–30 units on U-100) per dose — large enough to draw precisely but small enough to be comfortable subcutaneously. Use the BAC Water Optimizer above: enter your target dose and the calculator returns the exact water volume needed to achieve a 0.2 mL draw. A common starting point is 2 mL per 5 mg vial, yielding 2,500 mcg/mL, where a 500 mcg dose = 0.2 mL = 20 units.
How long does a reconstituted peptide vial remain stable?
Reconstituted peptides stored with bacteriostatic water and refrigerated at 2–8°C should be used within 28 days. After this point, the benzyl alcohol preservative becomes less effective and peptide degradation accelerates. Label every vial with the reconstitution date and discard after 28 days regardless of remaining volume. Never freeze a reconstituted solution — freeze-thaw cycles damage peptide structure.
Why does my draw show as imprecise in the table?
Any draw below 5 units on a U-100 syringe (0.05 mL) is too small to measure accurately. A one-unit error at 5 units = 20% dosing error. The fix: reconstitute with more BAC water to make a more dilute solution. Use the BAC Water Optimizer to find exactly how much water gives you 0.2 mL (20 units) per dose — 4× more precise and equally comfortable to inject.
What happens if I add the wrong amount of BAC water?
If you add too little, your concentration is higher than calculated — every dose you draw will contain more peptide than intended. If you add too much, concentration is lower and you get less peptide per draw. Always measure BAC water with a calibrated syringe (not by eye) and write the actual volume on the vial label immediately. If you've lost track, re-calculate using the actual volume you added rather than guessing.