Bacteriostatic water calculator
This bacteriostatic water calculator tells you how much water to add to a vial so each dose fills the number of units you choose on your syringe.
Bacteriostatic water to add
2mL
Add 2 mL so 250 mcg fills 10 units on a U-100 syringe.
- Rounded to 0.1 mL
- 2 mL → 10 units
- Concentration
- 2,500 mcg/mL (2.5 mg/mL)
- Each unit holds
- 25 mcg (0.025 mg)
- Full doses in the vial
- 20
- For 10 to 50 units per dose
- 2 to 10 mL
How does the bacteriostatic water calculator work?
It works backwards from the units you want to draw: water (mL) = vial (mcg) × units ÷ (dose (mcg) × units per mL). For a 5 mg vial, a 250 mcg dose and 10 units on a U-100 syringe, that is 5,000 × 10 ÷ (250 × 100) = 2 mL.
U-100 syringes have 100 units per mL, U-50 have 50 and U-40 have 40. The calculator converts mg to mcg for you and also shows the concentration, the amount in each unit and how many full doses the vial holds.
How much bacteriostatic water to add for a 10-unit dose
Water to add so each dose fills 10 units on a 1 mL U-100 syringe, calculated by this site.
| Vial | 100 mcg | 250 mcg | 500 mcg | 1,000 mcg |
|---|---|---|---|---|
| 2 mg | 2 | 0.8 | 0.4 | 0.2 |
| 5 mg | 5 | 2 | 1 | 0.5 |
| 10 mg | 10 | 4 | 2 | 1 |
| 15 mg | outside 0.1 to 10 mL | 6 | 3 | 1.5 |
– means the water would be under 0.1 mL or over 10 mL, or the dose is more than the vial holds.
How many units should each dose be?
Pick a round number that is easy to read on your syringe, like 10 or 20 units, and at least 2 units. Very small amounts are hard to measure accurately, and a dose over 100 units needs more than one 1 mL syringe.
Choosing the units first is the reverse of the usual approach. If you have already mixed your vial, use the peptide calculator to find the units for your dose instead. The choosing how much water to add guide explains the trade-offs.
Worked example: water for a 300 mcg dose
- Convert the vial to mcg: 5 mg × 1,000 = 5,000 mcg.
- Multiply by the units you want: 5,000 × 10 = 50,000.
- Divide by the dose times units per mL: 50,000 ÷ (300 × 100) = 1.6667 mL.
- Round to something you can measure: 1.7 mL, which makes the dose 10.2 units.
Frequently asked questions
How much bacteriostatic water do I add to a 5 mg vial?
It depends on your dose and how many units you want to draw. For a 250 mcg dose to fill 10 units on a U-100 syringe, add 2 mL. Enter your own numbers above for any other dose.
Does more water change the dose?
No. More water spreads the same amount of peptide through more liquid, so each dose takes more units. The dose in mcg stays the same.
What if the answer is an awkward amount like 1.67 mL?
Round to the nearest 0.1 mL and use the units the calculator shows for that amount. For example, 1.67 mL rounds to 1.7 mL, which makes a 300 mcg dose 10.2 units instead of 10.
Is bacteriostatic water the same as sterile water?
No. Bacteriostatic water contains 0.9% benzyl alcohol, which slows bacterial growth, so a vial can be used more than once. Sterile water has no preservative and is meant for single use.