Figure out exactly how much to draw on your syringe. Enter your vial, water, and dose below.
Bacteriostatic water (BAC water) is sterile water with 0.9% benzyl alcohol added as a preservative. It's used to reconstitute peptides because the preservative prevents bacterial growth, allowing the solution to be used over multiple doses. Never use regular water — always use bacteriostatic water or the diluent specified by the manufacturer.
The most common amount is 1–2 mL per vial. Using less water gives a more concentrated solution (fewer units per dose), while more water makes it easier to measure small doses accurately. There's no single right answer — use this calculator to see how your water volume affects the number of units per dose.
Insulin syringes come in 0.3 mL (30 units), 0.5 mL (50 units), and 1 mL (100 units). Smaller syringes are more precise for small doses. If your calculated dose is under 15 units, a 0.3 mL syringe gives you the best accuracy. For most peptide doses, a 0.5 mL or 1 mL syringe works well.
Most reconstituted peptides last 3–4 weeks when stored in the refrigerator (2–8°C / 36–46°F). Never freeze reconstituted peptides, and avoid leaving them at room temperature. Some peptides like semaglutide and tirzepatide may last longer — check the specific peptide's storage guidelines.
Adding too much water doesn't damage the peptide — it just makes the solution less concentrated, so you'll need to draw more per dose. Use this calculator to recalculate your dose with the actual water amount you added. The total peptide in the vial stays the same regardless of water volume.
This calculator is for informational and research purposes only. Not medical advice — consult a healthcare provider before using any peptide. Always verify your calculations before injecting anything.