BAC Water Calculator: How Much to Mix
Enter your vial strength and target dose — get exactly how much bacteriostatic water to add, in mL, plus the insulin units per dose. Works for Tirzepatide, Retatrutide, Semaglutide, and NAD+. Flip the toggle to go the other way if you already know your water amount.
Inputs
Results
to your 10mg Tirzepatide vial → each 2.5mg dose = 25 units on a U-100 insulin syringe (~4 doses per vial).
| BAC water | Units / dose | mg/mL |
|---|---|---|
| 0.5 mL | 12.5 IU | 20 |
| 1 mL ★ | 25 IU | 10 |
| 1.5 mL | 37.5 IU | 6.67 |
| 2 mL | 50 IU | 5 |
| 2.5 mL | 62.5 IU | 4 |
| 3 mL | 75 IU | 3.33 |
★ recommended — lands each dose in the easy-to-measure 10–50 IU range. More water ≠ more doses; it only spreads each dose over more units.
Pre-filled message includes your dose & vial spec — sales team gets context instantly.
The Reconstitution Formula
BAC water to add (solving for water)
BAC water (mL) = vial strength (mg) × dose volume (mL) ÷ target dose (mg)
Where dose volume = your desired insulin units ÷ 100. Water sets the concentration, so any volume works — pick one that lands each dose on an easy-to-read syringe marking (the calculator targets 10–50 units).
Concentration
concentration (mg/mL) = vial strength (mg) ÷ BAC water (mL)
Volume per dose
dose volume (mL) = target dose (mg) ÷ concentration (mg/mL)
Insulin syringe units
insulin units (IU) = dose volume (mL) × 100
Standard U-100 insulin syringe: 100 IU = 1.0 mL
Doses per vial
doses per vial = vial strength (mg) ÷ target dose (mg)
Frequently Asked Questions
How much bacteriostatic water do I mix with 10mg of tirzepatide?
For a 10mg tirzepatide vial, adding 2mL of bacteriostatic water gives a concentration of 5mg/mL. A 2.5mg dose then equals 0.5mL = 50 units on a U-100 insulin syringe, and the vial yields 4 doses. To make each dose land on an easier-to-read marking, use the calculator above — set vial to 10mg and your target dose, and it recommends the exact water volume.
How much bacteriostatic water do I mix with 5mg of semaglutide?
For a 5mg semaglutide vial dosed at 0.25mg per injection, adding 1mL of bacteriostatic water gives 5mg/mL, so 0.25mg = 0.05mL = 5 units. Because that is a very small draw, many add 2mL (2.5mg/mL → 0.1mL = 10 units) for easier measurement. Either way the vial yields 20 doses of 0.25mg — water volume changes the units per dose, not the number of doses.
How much bacteriostatic water do I mix with 20mg of retatrutide?
For a 20mg retatrutide vial dosed at 2mg, adding 2mL of bacteriostatic water gives 10mg/mL, so 2mg = 0.2mL = 20 units per dose, and the vial yields 10 doses. Set vial = 20mg and your target dose in the calculator above and it returns the recommended BAC water volume plus a chart of alternatives.
How does this BAC water / reconstitution calculator work?
Pick "How much water to add?" mode, then enter the vial strength (mg) and your target dose per injection (mg). The calculator recommends the bacteriostatic water volume that lands each dose in the easy-to-measure 10–50 unit range, and shows the concentration and doses per vial. Switch to "I know my water amount" mode to go the other way. Core formula: concentration = vial_mg / bac_water_ml; dose_volume_mL = target_dose_mg / concentration; insulin_units = dose_volume_mL × 100.
What does "100 IU = 1 mL" mean on an insulin syringe?
Standard U-100 insulin syringes are marked in IU (International Units). For peptide research, 100 IU on the syringe equals 1.0 mL of liquid: 50 IU = 0.5 mL, 10 IU = 0.1 mL. This calculator converts your dose volume to IU so you can draw the correct amount on a standard syringe.
What is bacteriostatic water and why is it used?
Bacteriostatic water (BAC water) is sterile water containing 0.9% benzyl alcohol as a preservative. It inhibits bacterial growth, allowing reconstituted peptide solutions to remain usable over multiple weeks when refrigerated. Sterile water (non-preserved) is also used but typically for single-day reconstitution.
Can I use this calculator for Tirzepatide, Semaglutide, Retatrutide, and NAD+?
Yes. The reconstitution math is identical for any lyophilized peptide vial. Only the typical vial strengths and dose ranges differ between compounds. The calculator includes presets for Tirzepatide (2.5–30mg), Semaglutide (0.25–1mg), Retatrutide (20mg), and NAD+ (100–500mg).
Where do I get the actual vials shown in this calculator?
Prost Biotech supplies research-grade Tirzepatide (2.5–30mg), Semaglutide (0.25–1mg), Retatrutide (20mg), NAD+ (100–500mg), and GHK-Cu (50mg) with ≥99% HPLC purity and batch-matched COA. After calculating, click "Get This Vial via WhatsApp" — the message is pre-filled with your spec for an instant bulk quote.
Research Use Only. This calculator provides reconstitution math for laboratory research. All peptide products sold by Prost Biotech are research chemicals — not for human consumption, therapeutic use, or clinical application. Consult licensed clinicians for personalized medical advice.