For research and educational purposes only. Peptides are not approved for human use unless specifically indicated. Read full disclaimer.
PeptideHub

BAC Water Calculator for Peptide Reconstitution

This calculator answers the most common reconstitution question: how much bacteriostatic water should I add? Enter your vial size and desired concentration — or any two of the three variables — and get the third instantly. A full reference table below covers the most common vial and water volume combinations.

Common research range for BPC-157: 250–500 mcg, 2× daily, subcutaneous. Cycle: 4 weeks on / 2 off.

Educational use only. This calculator performs unit math on the values you provide and is not a substitute for medical advice. Verify every calculation independently.

Result

Concentration
2500 mcg / mL
Per syringe unit
25.00 mcg / unit
Draw to this mark
15.0 units (0.15 mL)
Dose, all units
375 mcg · 0.375 mg
Doses per vial
13.3 doses
Days per vial
6.7 days
Vials needed for 4-week cycle
5 vials

Numbers are computed from your inputs. Verify all calculations independently. Educational use only.

How to Use This Calculator

  1. Identify your vial size: Check the label on your lyophilized peptide vial for the mass in mg (e.g., 5 mg, 10 mg). Enter this value in the calculator.
  2. Choose a target concentration: Decide what concentration (mcg/mL) you want after reconstitution. A round number like 1,000, 2,000, or 2,500 mcg/mL makes dose math easiest.
  3. Calculate required BAC water volume: The calculator solves: BAC water (mL) = vial mass (mcg) ÷ target concentration (mcg/mL). Enter any two values to solve for the third.
  4. Draw up the BAC water: Using a clean insulin syringe or a larger draw needle, pull the calculated volume of bacteriostatic water from the BAC water vial.
  5. Add to peptide vial slowly: Insert the needle and push the BAC water against the inside wall of the peptide vial. Do not spray directly onto the peptide cake. Swirl gently until dissolved.

Example Calculation

A researcher wants to reconstitute a 10 mg Ipamorelin vial to a concentration of 2,000 mcg/mL so that each 10 units on a U-100 syringe equals exactly 200 mcg.

  • Vial mass: 10 mg = 10,000 mcg
  • Target concentration: 2,000 mcg/mL
  • BAC water needed: 10,000 ÷ 2,000 = 5 mL
  • Units per 200 mcg dose: 200 ÷ (2,000 ÷ 100) = 10 units
  • Doses per vial: 10,000 ÷ 200 = 50 doses

BAC Water Reference Table

This table shows the resulting concentration for common vial sizes and BAC water volumes. Values rounded to the nearest whole number.

Vial Size1 mL BAC Water2 mL BAC Water3 mL BAC Water5 mL BAC Water
2 mg2,000 mcg/mL1,000 mcg/mL667 mcg/mL400 mcg/mL
5 mg5,000 mcg/mL2,500 mcg/mL1,667 mcg/mL1,000 mcg/mL
10 mg10,000 mcg/mL5,000 mcg/mL3,333 mcg/mL2,000 mcg/mL
15 mg15,000 mcg/mL7,500 mcg/mL5,000 mcg/mL3,000 mcg/mL
20 mg20,000 mcg/mL10,000 mcg/mL6,667 mcg/mL4,000 mcg/mL

mcg/mL = vial mass (mcg) ÷ BAC water volume (mL).

Frequently asked questions

How much BAC water should I add to a 5 mg peptide vial?+

For a 5 mg vial, 2 mL of bacteriostatic water is the most common choice among researchers. This gives a concentration of 2,500 mcg/mL and means each 10 units on a U-100 syringe equals 250 mcg — a clean, easy-to-read number for common peptide protocols.

What is bacteriostatic water?+

Bacteriostatic water (BAC water) is sterile water for injection preserved with 0.9% benzyl alcohol. The benzyl alcohol inhibits microbial growth, allowing the reconstituted vial to be used multiple times over approximately 30 days when stored at 2–8°C.

Can I use regular sterile water instead of BAC water?+

Sterile water for injection can be used but is intended for single use — it contains no preservative. If you plan to draw from the same vial more than once, bacteriostatic water is strongly preferred to reduce contamination risk.

Does more BAC water make the peptide weaker?+

No. Adding more BAC water lowers the concentration (mcg/mL) but does not degrade the peptide. The total amount of active compound in the vial stays the same. A lower concentration simply means you draw a larger volume for the same dose.

Why would I use less BAC water?+

Less water increases concentration, which means a smaller draw volume per dose. This can be useful when using very small syringes or when the target dose is very low and would otherwise require drawing a fractional unit that is hard to read.

How much BAC water comes in a standard vial?+

BAC water is typically sold in 30 mL multi-use vials. This is enough to reconstitute many peptide vials and is the format most commonly referenced in preclinical research contexts.

Can I mix BAC water from different batches?+

Researchers generally avoid mixing diluent from different vials into the same peptide solution to minimise potential contamination. Use one dedicated source of BAC water and discard it if it shows any cloudiness or particulate matter.