Peptide BAC Water Calculator — how much bacteriostatic water to add to a vial.
A free peptide BAC water calculator that tells you exactly how much bacteriostatic water to add to a research vial to hit a target concentration or a target dose per insulin-syringe unit. Enter the vial mass, pick your target, and read the BAC volume, resulting concentration, and syringe units with the formula visible.
Open the BAC water calculator Try the main peptide calculator
Free peptide BAC water calculator
Solve for the volume of bacteriostatic water to add to a research peptide vial. Type the vial mass, pick a target mode, and read the BAC volume in mL (and µL), the resulting concentration, dose volume per insulin mark and syringe units instantly.
Result — BAC water to add
What Is a Peptide BAC Water Calculator?
A peptide BAC water calculator is a tool that solves the question behind every first-time reconstitution: how much bacteriostatic water should I add to this vial? You type the mass of peptide inside the vial, pick a target — either a target concentration in mg/mL or a target dose per insulin-syringe unit — and the calculator returns the volume of BAC water to draw. Every intermediate value is shown alongside the answer so you can re-check the math by hand.
It is a different question from the peptide reconstitution calculator. The reconstitution calculator assumes you already know how much BAC water you want to add and reports the resulting concentration; the BAC water calculator assumes you know the concentration or dose you want and reports how much water to add. Both end at the same concentration, but the starting point is reversed.
How to Use the Peptide BAC Water Calculator
1. Enter the vial mass
Type the peptide mass contained in the vial — use mg for typical research vials (2 mg to 50 mg) or µg for very small ones. The unit selector converts automatically. The preset pills below the input cover the most common vial sizes.
2. Pick a target mode
Use By concentration when you have a target concentration in mind (mg/mL or µg/mL). Use By units per dose when you have a target dose per insulin-syringe mark (for example, 100 µg per U-100 mark). The calculator converts the target into a concentration and then computes the BAC volume.
3. Read the result
The result panel shows BAC water volume in mL and µL, the resulting concentration, the dose per syringe mark, the dose volume per mark, and the number of full doses the vial will yield. The animated pipette shows the BAC volume as a fraction of a 3 mL pipette. Use the action buttons to reset, copy the result, print a sheet, or copy a shareable URL.
How the BAC Water Math Works
Solving for BAC volume by concentration
V = m ÷ c
V is the BAC water volume in mL. m is the peptide mass in mg. c is the target concentration in mg/mL. Example: 10 mg ÷ 5 mg/mL = 2 mL. For µg and µg/mL inputs, convert to mg and mg/mL first.
Solving for BAC volume by units per dose
Each insulin-syringe mark holds a fixed volume in mL: U-100 = 0.01 mL, U-50 = 0.02 mL, U-30 ≈ 0.033 mL. If you want a specific dose per mark, the required concentration is the dose per mark divided by the volume per mark. Then the BAC volume is m ÷ c as above.
c = d ÷ vmark, then V = m ÷ c
Resulting dose volume per syringe unit
v = dose ÷ c
Once you know the resulting concentration, the dose volume for any chosen dose is dose ÷ concentration. In U-100 units, multiply by 100; in U-50, by 50; in U-30, by 30.
Overfill warning
The calculator compares the recommended BAC volume against the vial capacity you entered. If the result exceeds capacity, the calculator warns you. Real research vials often have a small overfill (a few percent) so the printed mass is recoverable even after accounting for dead volume in syringes.
How Much BAC Water Per Unit — Quick Reference
This table shows the dose per syringe mark for a few common target concentrations, on each of the three syringe scales.
| Target concentration | U-100 mark (0.01 mL) | U-50 mark (0.02 mL) | U-30 mark (≈0.033 mL) |
|---|---|---|---|
| 2 mg/mL | 20 µg/U | 40 µg/U | ≈66 µg/U |
| 5 mg/mL | 50 µg/U | 100 µg/U | ≈166 µg/U |
| 10 mg/mL | 100 µg/U | 200 µg/U | ≈333 µg/U |
| 20 mg/mL | 200 µg/U | 400 µg/U | ≈666 µg/U |
Quick Reference — Vial Size vs BAC Water
How much BAC water to add for a few common vial sizes at three standard target concentrations.
| Vial size | 2 mg/mL | 5 mg/mL | 10 mg/mL |
|---|---|---|---|
| 2 mg | 1.0 mL | 0.4 mL | 0.2 mL |
| 5 mg | 2.5 mL | 1.0 mL | 0.5 mL |
| 10 mg | 5.0 mL | 2.0 mL | 1.0 mL |
| 15 mg | 7.5 mL | 3.0 mL | 1.5 mL |
| 20 mg | 10.0 mL | 4.0 mL | 2.0 mL |
| 30 mg | 15.0 mL | 6.0 mL | 3.0 mL |
| 50 mg | 25.0 mL | 10.0 mL | 5.0 mL |
Mathematical Examples
Example 1 — 10 mg vial at 5 mg/mL (Mathematical Example)
V = 10 ÷ 5 = 2.000 mL of BAC water. Resulting concentration: 5 mg/mL. On a U-100 syringe: 50 µg per mark. Total doses if drawing 500 µg each: 20.
Example 2 — 10 mg vial with 100 µg per U-100 mark
Required concentration = 100 µg ÷ 0.01 mL = 10 mg/mL. V = 10 ÷ 10 = 1.000 mL BAC water. Each U-100 mark now draws 100 µg.
Example 3 — 5 mg vial at 2.5 mg/mL
V = 5 ÷ 2.5 = 2.000 mL BAC water. Resulting concentration: 2.5 mg/mL. On U-100: 25 µg per mark. Total doses at 250 µg each: 20.
Example 4 — 15 mg vial at 250 µg per U-100 mark
Required concentration = 250 µg ÷ 0.01 mL = 25 mg/mL. V = 15 ÷ 25 = 0.600 mL BAC water (600 µL). Each U-100 mark draws 250 µg. Total doses: 60.
Example 5 — 50 mg vial at 0.5 mg per U-100 mark
Required concentration = 500 µg ÷ 0.01 mL = 50 mg/mL. V = 50 ÷ 50 = 1.000 mL BAC water. Each U-100 mark draws 500 µg. Total doses: 100.
Common Peptide BAC Water Mistakes
The calculator uses the value you type as the peptide mass in the vial. If the label says 10 mg per vial, type 10. If the certificate of analysis says 10.2 mg with overfill, type 10.2.
Targeting a very high concentration to keep the BAC volume small is mathematically correct but physically impossible if the BAC volume is below the volume your syringe can measure accurately.
1 mg/mL = 1000 µg/mL. A target of 5000 µg/mL is the same as 5 mg/mL. Always read the unit selector.
The BAC volume the calculator returns is the volume that ends up in solution. Real syringes retain a small dead volume, so you may need to draw slightly more than the calculated value.
Peptide BAC Water Calculator FAQ
What does a peptide BAC water calculator do?
It solves for how much bacteriostatic water to add to a peptide vial to reach a target concentration (mg/mL) or a target dose per insulin unit (µg per U-100 mark).
How is BAC water volume calculated from a target concentration?
V = m ÷ c, where V is the BAC water volume in mL, m is the peptide mass in mg, and c is the target concentration in mg/mL.
How much BAC water for a 10 mg vial?
10 mg ÷ 5 mg/mL = 2 mL; 10 mg ÷ 10 mg/mL = 1 mL; 10 mg ÷ 2 mg/mL = 5 mL.
How is BAC water volume calculated from a target dose per unit?
For a U-100 syringe, each mark is 0.01 mL. The required concentration is dose per mark ÷ 0.01 mL, then BAC water = peptide mass ÷ concentration.
Can I use sterile water instead of BAC water?
Sterile water can be used to reconstitute peptides, but it does not contain the bacteriostatic preservative that BAC water carries.
How much water do I add to a peptide for a 100 unit syringe?
For a U-100 syringe, target concentration in mg/mL = µg per mark ÷ 10.
What if the calculator says I need 6 mL of BAC water but my vial only holds 5 mL?
Either pick a higher target concentration or split the peptide across two vials.
Does the BAC water calculator account for overfill in the vial?
No. The calculator uses the mass printed on the vial label.
Can I save my inputs and come back later?
Click Share Link. The button copies a URL with your inputs as query parameters; open it later to restore values.
Is this calculator a substitute for medical advice?
No. The peptide BAC water calculator is a math tool only.
Related Peptide Calculators
The peptide BAC water calculator on this page performs mathematical conversions only. It does not give medical advice, recommend a dose for any person or animal, or model pharmacokinetics. Read the full medical disclaimer and the site disclaimer.