Peptide Reconstitution Calculator

Educational tool for reconstituting lyophilized peptide vials with bacteriostatic (BAC) water. Forward mode converts a peptide amount and BAC water volume into a concentration plus the volume per dose. Reverse mode solves for the BAC water volume that lands a target dose at a chosen draw size (mL or U-100 units).

New here? See a worked example

How it works

Two ways to use it. Forward mode answers "I added X mL of BAC water - what do I draw?". Reverse mode answers "I want my dose to land at this many units - how much BAC water should I add?".

Enter your peptide vial size
Type the amount of peptide in the vial in milligrams - typically 2 mg, 5 mg, 10 mg, or 15 mg.
Enter how much BAC water you added
In forward mode, type the volume of bacteriostatic water you added (commonly 1, 2, or 3 mL). The calculator works out the resulting concentration.
Enter your target dose
Type the dose you want to inject. Most peptides are dosed in micrograms - the calculator lets you switch units between mg and mcg.
Read the volume to draw and the syringe marking
You get the final concentration in mg/mL, the volume to draw in mL, the matching marking on a U-100 insulin syringe, and how many doses the vial provides.

Worked example

5 mg vial reconstituted with 2 mL of BAC water, 250 mcg dose

Peptide vial: 5 mg
BAC water added: 2 mL
Target dose: 250 mcg (0.25 mg)

Final concentration: 2.5 mg/mL
Volume to draw: 0.10 mL
U-100 syringe units: 10 units
Doses per vial: 20 doses

Each 250 mcg dose works out to 0.10 mL - the 10-unit mark on a U-100 insulin syringe. A reconstituted 5 mg vial gives you 20 doses at that level. Always label the vial with concentration, date, and storage location after reconstitution.

Show the underlying formulas

1. Final volume (mL)
final_volume_mL = bac_water_mL + displacement_mL
2. Concentration (mg/mL)
concentration_mg_per_mL = peptide_vial_mg / final_volume_mL
3. Draw per dose (mL)
draw_mL = target_dose_mg / concentration_mg_per_mL
4. U-100 syringe units (estimate)
units = draw_mL * 100
5. Reverse mode: BAC water needed
bac_water_mL = (peptide_vial_mg * desired_draw_mL / target_dose_mg) - displacement_mL
6. Doses per vial
doses_per_vial = floor(peptide_vial_mg / target_dose_mg)
7. Days of supply
days_of_supply = doses_per_vial * interval_days

Full citations and assumptions: see methodology page.

Frequently asked questions

What does the peptide reconstitution calculator do?

It converts a lyophilised peptide vial (in mg) plus a volume of bacteriostatic water (in mL) into a final concentration (mg/mL), the volume to draw per dose, and an estimated U-100 syringe unit marking. It also runs in reverse: given a target dose and a desired draw size, it tells you how much BAC water to add so the dose lands at the marking you want.

How much BAC water do I add to a 5 mg vial of BPC-157?

Adding 2 mL of BAC water to a 5 mg vial gives you 2.5 mg/mL. A 250 mcg dose is then 0.10 mL - 10 units on a U-100 insulin syringe. Adjust the BAC water input in the calculator to land on whatever draw size your protocol calls for.

What is powder displacement and when does it matter?

Powder displacement is the volume the dry peptide itself occupies in the vial after BAC water is added. For most peptides it is small (well under 0.1 mL) and the default is 0 mL. Enable it under Advanced if your peptide ships with a known displacement value - it will tighten the concentration math on small vials with high mg loads.

What is the difference between forward mode and reverse mode?

Forward mode answers "I added X mL of BAC water - what do I draw?". Reverse mode answers "I want my dose to land at N units / Y mL - how much BAC water should I add?". Reverse mode is useful when your protocol calls for a specific draw size on the syringe so you don't have to measure tiny volumes.

How long does a reconstituted peptide vial last?

This calculator does not determine beyond-use dates, sterility, or stability. Storage life depends on the peptide, the BAC water preservative, refrigeration, and light exposure - always follow your prescribing professional's guidance and label every vial with concentration, date, and storage location after reconstitution.

Why are peptide doses sometimes in mcg and sometimes in mg?

Most peptides are dosed in micrograms (mcg) because effective doses are very small (often 100 - 500 mcg). The calculator lets you toggle between mg and mcg for the dose input so you can match your protocol exactly. Internally everything is converted to mg for the math (1 mg = 1000 mcg).

Does the calculator validate that my dose is safe?

No - it performs unit conversion and concentration math only. It does not know which peptide you are working with, what a safe protocol looks like, or whether a draw is reasonable for your situation. Always work with a licensed clinician and follow vetted protocol guidance.

How should I label a reconstituted vial?

At minimum: peptide name, final concentration (mg/mL), reconstitution date, and storage location. Many users also note the BAC water lot number. Labelling protects against mix-ups when you have multiple peptides reconstituted at the same time.