The amount of BAC water to add depends on your vial amount and how much you want to measure. As an example, adding 2 mL to a 5 mg BPC-157 vial makes 2.5 mg/mL, so measuring 250 mcg comes out to 10 units on a U-100 syringe. Use the calculator below for your exact numbers.
How much BAC water do I add?
Tell us your peptide, vial amount, and how much you want to measure. We'll tell you exactly how much bacteriostatic water to add so your syringe math comes out clean and easy to measure.
Which peptide?
What size is your vial?
Look at the number printed on your vial label. It tells you how much peptide powder is inside.
How much do you measure each time?
Enter how much you want to measure each time, in mg or mcg.
Enter a vial amount and how much you want to measure to see exactly how much bac water to add.
This is general reconstitution math for research and educational use only. BACwater.ai is not a medical company, and this is not medical advice. Always check your product's own paperwork and talk to your doctor before making any health decision. Read the full disclaimer.
What is bacteriostatic water?
Bacteriostatic water (BAC water) is sterile water with a tiny amount of benzyl alcohol (0.9%) added. The benzyl alcohol prevents bacteria from growing, which means your reconstituted peptide stays safe to use for weeks instead of hours.
You can't use tap water, bottled water, or regular sterile water. Only BAC water is designed for this purpose.
What does “reconstitute” mean?
Peptides arrive as a dry powder inside a sealed vial. Before you can measure an amount, you need to dissolve the powder in liquid. That process is called reconstitution. You add BAC water to the vial, swirl gently, and the powder dissolves into a clear solution.
Why does the amount of water matter?
The amount of water you add determines the concentration of the solution: how much peptide is in each drop of liquid. More water means a weaker solution (you measure more each time). Less water means a stronger solution (you measure less each time).
We pick an amount that makes each measurement land on a round, easy-to-read number on your syringe. No squinting at tiny lines, no guessing between markings.
Related guides
Quick reference
| Vial amount | Bac water to add | Example measurement | Units |
|---|---|---|---|
| 2 mg | 1 mL | 100 mcg | 5 units |
| 5 mg | 2 mL | 250 mcg | 10 units |
| 10 mg | 2 mL | 500 mcg | 10 units |
| 15 mg | 3 mL | 500 mcg | 10 units |
Examples that put a measurement at a clean syringe mark. Use the calculator above for your exact vial and amount.
Related questions
How much bac water for a 5 mg vial?
A common starting point is 2 mL of bacteriostatic water for a 5 mg vial. That gives 2.5 mg/mL, so measuring 250 mcg is 10 units on a U-100 syringe. Adjust the water to move the measurement to an easier mark.
Can you add too much bac water?
Adding more is not a safety problem, but it makes each measurement a larger volume to measure. Too little makes the measurement a very small, hard-to-measure volume. Aim for a measurement that lands near a round number of units.
Does adding more bac water change how much peptide you get?
No. More bac water lowers the concentration, so you measure a larger volume for the same amount of peptide. The amount of peptide stays the same; only the volume you measure changes.