Bacteriostatic water calculator
BAC Water Calculator
Pick the number of units you want each dose to be. The calculator tells you how much bacteriostatic water to add to the vial to make that happen.
BAC water calculator
Example values are loaded. Replace them with the numbers on your own vial.
Why plan the water first
You choose the water volume once, when you mix the vial, and it sets every draw after that. Choosing it so the dose lands on a round number (10, 20 or 25 units) means you read the same clear line on the syringe every time instead of estimating between marks.
The formula
Example: you have a 10 mg vial and want a 2 mg dose to equal 20 units. Water = (20 ÷ 100) × 10 ÷ 2 = 1 mL. Check: 10 mg in 1 mL is 10 mg/mL, and 2 mg is 0.2 mL, which is 20 units.
Practical limits
- Vial size. Most small peptide vials hold about 3 to 10 mL. If the calculator asks for more water than the vial can take, pick a larger unit target or a smaller one-vial plan.
- Syringe size. A target above 30 units will not fit a 0.3 mL syringe; above 50 units will not fit a 0.5 mL syringe.
- Very small targets. Draws under about 2 units are hard to measure. The table under the result shows how the draw changes with each water volume.
The difference between bacteriostatic water and sterile water, and why it matters for vials you draw from more than once, is covered in bacteriostatic water vs sterile water.
Frequently asked questions
How much bacteriostatic water do I add to a 10 mg vial?
It depends on the dose and how many units you want each dose to be. For example, to make a 2 mg dose equal 20 units, add 1 mL. To make it 40 units, add 2 mL. Enter your numbers above for the exact amount.
Does the amount of water change the dose?
No. Water changes the concentration, not the total amount of peptide. The dose in mg stays the same; only the volume you draw changes.
Can I use sterile water instead of bacteriostatic water?
Sterile water contains no preservative and is meant for single use. Bacteriostatic water contains 0.9% benzyl alcohol, which limits bacterial growth in a vial that is punctured several times. Follow the instructions that come with your product.