Peptide Calculator

Q: Can I use sterile water instead of bacteriostatic water?

Sterile water contains no preservative. Bacteriostatic water contains 0.9% benzyl alcohol, which suppresses microbial growth and makes multi-dose use more practical.

Step 1 — Reconstitution

Vial Size

BAC Water

Target Dose

mcg

Quick Fill

Step 2 — Syringe

Draw To
—
units (IU)

Volume

—

Doses / Vial

—

doses

Vial Lasts

—

weeks

U-100 Syringe 100 Unit

Exact mark.

—

Draw — units

Summary

Concentration

—

mg per mL

Dose Per Injection

—

mcg

Per Unit

—

mcg per IU

Total Doses

—

doses per vial

Quick Reference

Peptide	Vial	BAC	Conc.	Per Unit
BPC-157	5mg	2mL	2.5mg/mL	25mcg
TB-500	10mg	2mL	5mg/mL	50mcg
Retatrutide	10mg	2mL	5mg/mL	50mcg
Semaglutide	5mg	2mL	2.5mg/mL	25mcg
Ipamorelin	5mg	2mL	2.5mg/mL	25mcg
CJC-1295	2mg	1mL	2mg/mL	20mcg
PT-141	10mg	2mL	5mg/mL	50mcg
Tesamorelin	10mg	2mL	5mg/mL	50mcg

What Is Peptide Reconstitution?

Peptide reconstitution is the process of dissolving a lyophilized (freeze-dried) peptide powder in a liquid — typically bacteriostatic water — to create a solution of a known concentration. Manufacturers freeze-dry research peptides because removing water dramatically slows the chemical reactions that would otherwise degrade the peptide, letting the dry powder remain stable in storage far longer than a solution would.

To reconstitute, sterile bacteriostatic water is added slowly to the vial and allowed to dissolve the powder without vigorous shaking. Once mixed, the peptide solution should be stored cold and away from light, because reconstituted peptides are far less stable than their dry form and begin to degrade over days to weeks.

The exact concentration of the finished solution — and therefore every dose you draw from it — is fixed the moment you decide how much water to add. That is precisely the number this calculator helps you plan.

How Much Bacteriostatic Water Should You Use?

The volume of bacteriostatic water you add does not change the total amount of peptide in the vial — it only changes the concentration of the solution. A 5 mg vial contains 5 mg of peptide whether you add 1 mL or 3 mL of water. More water simply spreads that same 5 mg across a larger volume, so each unit on the syringe carries less peptide.

More water = larger, easier-to-measure draw   |   Less water = higher concentration, smaller draw

Bacteriostatic water contains 0.9% benzyl alcohol, a preservative that suppresses microbial growth and lets a vial be drawn from repeatedly over its usable life. A reconstituted vial should be swirled gently rather than shaken and kept refrigerated.

Understanding Concentration: mcg, mg, and mL

Concentration is the amount of peptide contained in each milliliter of solution, written as mg/mL or mcg/mL. It is the single value that connects your vial to your syringe:

Concentration (mg/mL) = peptide amount (mg) ÷ water volume (mL)

Adding 2 mL of bacteriostatic water to a 5 mg vial gives a concentration of 2.5 mg/mL.

Two key conversions

1 mg = 1,000 mcg — doses written in micrograms and vials written in milligrams share one scale
U-100 syringe: 100 units = 1 mL, so 1 unit = 0.01 mL

Reading the Syringe: Units, Draw Volume & Barrel Size

An insulin syringe on the U-100 scale holds 100 units per milliliter. The number of units to draw is:

Units = draw volume (mL) × 100

A 0.1 mL draw = 10 units. A 0.05 mL draw = 5 units.

Barrel size is where accuracy is won or lost

30-unit (0.3 mL) — graduated every 0.5 units: most accurate for small draws
50-unit (0.5 mL) — graduated every 1 unit: mid-range draws
100-unit (1.0 mL) — graduated every 2 units: largest draws

Studies of small-volume measurement show that percent error grows as the measured volume becomes a smaller fraction of the syringe's capacity. Matching barrel size to the volume being measured meaningfully improves accuracy.

Worked Example: Reconstituting a 5 mg Vial

Scenario — BPC-157 · 5mg Vial · 2mL BAC Water

Concentration: 5 mg ÷ 2 mL = 2.5 mg/mL (2,500 mcg/mL)

Per unit: 2,500 mcg/mL ÷ 100 units = 25 mcg per unit

250 mcg dose: 250 mcg ÷ 2,500 mcg/mL = 0.1 mL = 10 units

Doses per vial: 5,000 mcg ÷ 250 mcg = 20 doses

Why Accurate Dosage Calculation Matters

Because research peptides are dosed in micrograms and drawn in fractions of a milliliter, a small measurement slip represents a large percentage of the intended dose.

The calculator removes the guesswork from every draw — making every dose consistent with the last.

How to Use This Calculator

Enter the peptide vial amount. Type the total peptide on the vial label (e.g. 5 mg or 10 mg).
Enter the BAC water volume. Choose the volume you plan to add, in milliliters.
Enter your target dose. Type your desired dose and choose mcg or mg. Quick Fill buttons populate common peptide protocols in one tap.
Choose your syringe size. Select the 30-, 50-, or 100-unit insulin syringe you are using.
Read your draw. The results show the exact units, volume in mL, and how many doses the vial holds.

Frequently Asked Questions

How much bacteriostatic water should I add to a peptide vial?

There is no single correct volume — the amount of water sets the concentration, not the dose. More water gives a larger, easier-to-measure draw; less water gives a higher concentration and a smaller draw. Common choices are 1 mL, 2 mL, and 3 mL.

How do I calculate a peptide dose in units?

Divide your desired dose by the solution's concentration to get the draw volume in milliliters, then multiply by 100 to get units on a U-100 insulin syringe. This calculator runs the conversion automatically.

What syringe size is best for peptides?

Match the barrel to your draw. A 30-unit (0.3 mL) syringe has the finest marks for small doses. A 50-unit (0.5 mL) suits mid-range draws. A 100-unit (1.0 mL) fits the largest draws. The calculator recommends the smallest barrel that fits your dose.

How long does a reconstituted peptide vial last?

Once reconstituted, a peptide solution is far less stable than the dry powder and should be kept refrigerated and away from light. Reconstituted research peptides are generally used within a few weeks.

Can I use sterile water instead of bacteriostatic water?

Sterile water contains no preservative, so a vial reconstituted with it offers no protection against microbial growth once opened. Bacteriostatic water contains 0.9% benzyl alcohol, which suppresses microbial growth and makes multi-dose use more practical.

How do I convert mcg to mL?

Divide the dose in micrograms by the concentration in mcg/mL to get the volume in milliliters. This is exactly what this calculator does automatically.

References

Lau, J. L. & Dunn, M. K. (2018). Therapeutic peptides: Historical perspectives, current development trends, and future directions. Bioorganic & Medicinal Chemistry, 26(10), 2700–2707.

Muttenthaler, M. et al. (2021). Trends in peptide drug discovery. Nature Reviews Drug Discovery, 20(4), 309–325.

Manning, M. C., Patel, K. & Borchardt, R. T. (1989). Stability of protein pharmaceuticals. Pharmaceutical Research, 6(11), 903–918.

Stroppel, L. et al. (2023). Antimicrobial preservatives for protein and peptide formulations. Pharmaceutics, 15(2), 563.

Jordan, M. A. et al. (2021). Development of guidelines for accurate measurement of small volume parenteral products. Hospital Pharmacy, 56(3), 165–171.

Gnanalingham, M. G. et al. (1998). Accuracy and reproducibility of low dose insulin administration using pen-injectors and syringes. Archives of Disease in Childhood, 79(1), 59–62.